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Hyperbola

Class 11th Mathematics RD Sharma Solution
Exercise 27.1
  1. The equation of the directrix of a hyperbola is x - y + 3 = 0. Its focus is…
  2. vertices (0, ± 6), e = 5/3 In each of the following find the equations of the…
  3. focus is (0, 3), directrix is x + y - 1 = 0 and eccentricity = 2 Find the…
  4. focus is (1, 1), directrix is 3x + 4y + 8 = 0 and eccentricity = 2 Find the…
  5. focus is (1, 1) directrix is 2x + y = 1 and eccentricity = root 3 Find the…
  6. focus is (2, -1), directrix is 2x + 3y = 1 and eccentricity = 2 Find the…
  7. focus is (a, 0), directrix is 2x + 3y = 1 and eccentricity = 2 Find the…
  8. focus is (2, 2), directrix is x + y = 9 and eccentricity = 2 Find the equation…
  9. 9x^2 - 16y^2 = 144 Find the eccentricity, coordinates of the foci, equations…
  10. 16x^2 - 9y^2 = -144 Find the eccentricity, coordinates of the foci, equations…
  11. 4x^2 - 3y^2 = 36 Find the eccentricity, coordinates of the foci, equations of…
  12. 3x^2 - y^2 = 4 Find the eccentricity, coordinates of the foci, equations of…
  13. 2x^2 - 3y^2 = 5 Find the eccentricity, coordinates of the foci, equations of…
  14. Find the axes, eccentricity, latus-rectum and the coordinates of the foci of…
  15. 16x^2 - 9y^2 + 32x + 36y - 164 = 0 Find the centre, eccentricity, foci and…
  16. x^2 - y^2 + 4x = 0 Find the centre, eccentricity, foci and directions of the…
  17. x^2 - 3y^2 - 2x = 8 Find the centre, eccentricity, foci and directions of the…
  18. the distance between the foci = 16 and eccentricity = root 2 Find the equation…
  19. conjugate axis is 5 and the distance between foci = 13 Find the equation of…
  20. conjugate axis is 7 and passes through the point (3, -2). Find the equation of…
  21. foci are (6, 4) and (-4, 4) and eccentricity is 2. Find the equation of the…
  22. vertices are (-8, -1) and (16, -1) and focus is (17, -1) Find the equation of…
  23. foci are (4, 2) and (8, 2) and eccentricity is 2. Find the equation of the…
  24. vertices are at (0. ± 7) and foci at (0 , plus or minus 28/3) Find the…
  25. vertices are at (±6, 0) and one of the directrices is x = 4. Find the equation…
  26. foci at (± 2, 0) and eccentricity is 3/2. Find the equation of the hyperbola…
  27. Find the eccentricity of the hyperbola, the length of whose conjugate axis is…
  28. the focus is at (5, 2), vertices at (4, 2) and (2, 2) and centre at (3, 2)…
  29. focus is at (4, 2), centre at (6, 2) and e = 2. Find the equation of the…
  30. If P is any point on the hyperbola whose axis are equal, prove that SP.S’P =…
  31. vertices (± 2, 0), foci (± 3, 0) In each of the following find the equations…
  32. vertices (0, ± 5), foci (0, ± 8) In each of the following find the equations…
  33. vertices (0, ± 3), foci (0, ± 5) In each of the following find the equations…
  34. foci (±5, 0), transverse axis = 8 In each of the following find the equations…
  35. foci (0, ±13), conjugate axis = 24 In each of the following find the…
  36. foci (plus or minus 3 root 5 , 0) , the latus-rectum = 8 In each of the…
  37. foci (±4, 0), the latus-rectum = 12 In each of the following find the…
  38. foci (0 , plus or minus root 10) , passing through (2, 3) In each of the…
  39. foci (0, ± 12), latus-rectum = 36. In each of the following find the…
  40. If the distance between the foci of a hyperbola is 16 and its eccentricity is…
  41. Show that the set of all points such that the difference of their distances…
Very Short Answer
  1. Write the eccentricity of the hyperbola 9x^2 - 16y^2 = 144.
  2. Write the eccentricity of the hyperbola whose latus-rectum is half of its transverse…
  3. Write the coordinates of the foci of the hyperbola 9x^2 - 16y^2 = 144.…
  4. Write the equation of the hyperbola of eccentricity root 2 , if it is known that the…
  5. If the foci of the ellipse x^2/16 + y^2/b^2 = 1 and the hyperbola x^2/144 - y^2/81 =…
  6. Write the length of the latus-rectum of the hyperbola 16x^2 - 9y^2 = 144.…
  7. If the latus-rectum through one focus of a hyperbola subtends a right angle at the…
  8. Write the distance between the directrices of the hyperbola x = 8 sec θ, y = 8 tan θ.…
  9. Write the equation of the hyperbola whose vertices are (±3, 0) and foci at (±5, 0).…
  10. If e1 and e2 are respectively the eccentricities of the ellipse x^2/18 + y^2/4 = 1 and…
Mcq
  1. Equation of the hyperbola whose vertices are (± 3, 0) and foci at (± 5, 0), isA. 16x^2…
  2. If e1 and e2 are respectively the eccentricities of the ellipse x^2/18 + y^2/4 = 1 and…
  3. The distance between the directrices of the hyperbola x = 8 sec θ, y = 8 tan θ, isA. 8…
  4. The equation of the conic with focus at (1, -1) directrix along x - y + 1= 0 and…
  5. The eccentricity of the conic 9x^2 - 16y^2 = 144 isA. 5/4 B. 4/3 C. 4/5 D. root 7…
  6. The latus-rectum of the hyperbola 16x^2 - 9y^2 = 144 isA. 16/3 B. 32/3 C. 8/3 D. 4/3…
  7. A point moves in a plane so that its distances PA and PB from two fixed points A and B…
  8. The eccentricity of the hyperbola whose latus-rectum is half of its transverse axis,…
  9. The eccentricity of the hyperbola x^2 - 4y^2 = 1 isA. root 3/2 B. root 5/2 C. 2/root 3…
  10. The difference of the focal distances of any point on the hyperbola is equal toA.…
  11. the foci of the hyperbola 9x^2 - 16y^2 = 144 areA. (± 4, 0) B. (0, ± 4) C. (± 5, 0) D.…
  12. The distance between the foci of a hyperbola is 16 and its eccentricity is root 2 ,…
  13. If e1 is the eccentricity of the conic 9x^2 + 4y^2 = 36 and e2 is the eccentricity of…
  14. If the eccentricity of the hyperbola x^2 - y^2 sec^2 ∝ = 5 is root 3 times the…
  15. The equation of the hyperbola whose foci are (6, 4) and (-4, 4) and eccentricity 2,…
  16. The length of the straight line x - 3y = 1 intercepted by the hyperbola x^2 - 4y^2 = 1…
  17. The foci of the hyperbola 2x^2 - 3y^2 = 5 areA. (plus or minus 5 root 6 , 0) B. (±…
  18. The eccentricity the hyperbola x = a/2 (t + 1/t) , y = a/2 (t - 1/t) isA. root 2 B.…
  19. The equation of the hyperbola whose centre is (6, 2) one focus is (4, 2) and of…
  20. The locus of the point of intersection of the lines root 3x-y-4 root 3 lambda = 0 and…

Exercise 27.1
Question 1.

The equation of the directrix of a hyperbola is x – y + 3 = 0. Its focus is (-1, 1) and eccentricity 3. Find the equation of the hyperbola.


Answer:

Given: Equation of directrix of a hyperbola is x – y + 3 = 0. Focus of hyperbola is (-1, 1) and eccentricity (e) = 3


To find: equation of the hyperbola


Let M be the point on directrix and P(x, y) be any point of the hyperbola


Formula used:



where e is an eccentricity, PM is perpendicular from any point P on hyperbola to the directrix


Therefore,




Squaring both sides:




{∵ (a – b)2 = a2 + b2 + 2ab &


(a + b + c)2 = a2 + b2 + c2 + 2ab + 2bc + 2ac}


⇒ 2{x2 + 1 + 2x + y2 + 1 – 2y} = 9{x2 + y2+ 9 + 6x – 6y – 2xy}


⇒ 2x2 + 2 + 4x + 2y2 + 2 – 4y = 9x2 + 9y2+ 81 + 54x – 54y – 18xy


⇒ 2x2 + 4 + 4x + 2y2– 4y – 9x2 - 9y2 - 81 – 54x + 54y + 18xy = 0


⇒ – 7x2 - 7y2 – 50x + 50y + 18xy – 77 = 0


7x2 + 7y2 + 50x – 50y – 18xy + 77 = 0


This is the required equation of hyperbola




Question 2.

In each of the following find the equations of the hyperbola satisfying the given conditions

vertices (0, ± 6),


Answer:

Given: Vertices (0, ±6),


To find: equation of the hyperbola


Formula used:


The standard form of the equation of the hyperbola is,



Coordinates of the vertices for a standard hyperbola is given by (0, ±b)


According to question:


b = 6 ⇒ b2 = 36


We know,


a2 = b2(e2 – 1)







⇒ a2 = 64


Hence, equation of hyperbola is:





Question 3.

Find the equation of the hyperbola whose

focus is (0, 3), directrix is x + y – 1 = 0 and eccentricity = 2


Answer:

Given: Equation of directrix of a hyperbola is x + y – 1 = 0. Focus of hyperbola is (0, 3) and eccentricity (e) = 2


To find: equation of the hyperbola


Let M be the point on directrix and P(x, y) be any point of the hyperbola


Formula used:



where e is an eccentricity, PM is perpendicular from any point P on hyperbola to the directrix


Therefore,




Squaring both sides:




{∵ (a – b)2 = a2 + b2 + 2ab &


(a + b + c)2 = a2 + b2 + c2 + 2ab + 2bc + 2ac}


⇒ 2{x2 + y2 + 9 – 6y} = 4{x2 + y2 + 1 – 2x – 2y + 2xy}


⇒ 2x2 + 2y2 + 18 – 12y = 4x2 + 4y2+ 4 – 8x – 8y + 8xy


⇒ 2x2 + 2y2 + 18 – 12y – 4x2 – 4y2 – 4 – 8x + 8y – 8xy = 0


⇒ – 2x2 – 2y2 – 8x – 4y – 8xy + 14 = 0


⇒ -2(x2 + y2 – 4x + 2y + 4xy – 7) = 0


x2 + y2 – 4x + 2y + 4xy – 7 = 0


This is the required equation of hyperbola




Question 4.

Find the equation of the hyperbola whose

focus is (1, 1), directrix is 3x + 4y + 8 = 0 and eccentricity = 2


Answer:

Given: Equation of directrix of a hyperbola is 3x + 4y + 8 = 0. Focus of hyperbola is (1, 1) and eccentricity (e) = 2


To find: equation of hyperbola


Let M be the point on directrix and P(x, y) be any point of hyperbola


Formula used:



where e is eccentricity, PM is perpendicular from any point P on hyperbola to the directrix


Therefore,




Squaring both sides:




{∵ (a – b)2 = a2 + b2 + 2ab &


(a + b + c)2 = a2 + b2 + c2 + 2ab + 2bc + 2ac}


⇒ 25{x2 + 1 – 2x + y2 + 1 – 2y} = 4{9x2 + 16y2+ 64 + 24xy + 64y + 48x}


⇒ 25x2 + 25 – 50x + 25y2 + 25 – 50y = 36x2 + 64y2 + 256 + 96xy + 256y + 192x


⇒ 25x2 + 25 – 50x + 25y2 + 25 – 50y – 36x2 – 64y2 – 256 – 96xy – 256y – 192x = 0


⇒ – 11x2 – 39y2 – 242x – 306y – 96xy – 206 = 0


11x2 + 39y2 + 242x + 306y + 96xy + 206 = 0


This is the required equation of hyperbola




Question 5.

Find the equation of the hyperbola whose

focus is (1, 1) directrix is 2x + y = 1 and eccentricity =


Answer:

Given: Equation of directrix of a hyperbola is 2x + y – 1 = 0. Focus of hyperbola is (1, 1) and eccentricity (e) =


To find: equation of hyperbola


Let M be the point on directrix and P(x, y) be any point of hyperbola


Formula used:



where e is eccentricity, PM is perpendicular from any point P on hyperbola to the directrix


Therefore,




Squaring both sides:




{∵ (a – b)2 = a2 + b2 + 2ab &


(a + b + c)2 = a2 + b2 + c2 + 2ab + 2bc + 2ac}


⇒ 5{x2 + 1 – 2x + y2 + 1 – 2y} = 3{4x2 + y2+ 1 + 4xy – 2y – 4x}


⇒ 5x2 + 5 – 10x + 5y2 + 5 – 10y = 12x2 + 3y2 + 3 + 12xy – 6y – 12x


⇒ 5x2 + 5 – 10x + 5y2 + 5 – 10y – 12x2 – 3y2 – 3 – 12xy + 6y + 12x = 0


⇒ – 7x2 + 2y2 + 2x – 4y – 12xy + 7 = 0


7x2 – 2y2 – 2x + 4y + 12xy – 7 = 0


This is the required equation of hyperbola.




Question 6.

Find the equation of the hyperbola whose

focus is (2, -1), directrix is 2x + 3y = 1 and eccentricity = 2


Answer:

Given: Equation of directrix of a hyperbola is 2x + 3y – 1 = 0. Focus of hyperbola is (2, -1) and eccentricity (e) = 2


To find: equation of hyperbola


Let M be the point on directrix and P(x, y) be any point of hyperbola


Formula used:



where e is eccentricity, PM is perpendicular from any point P on hyperbola to the directrix


Therefore,




Squaring both sides:




{∵ (a – b)2 = a2 + b2 + 2ab &


(a + b + c)2 = a2 + b2 + c2 + 2ab + 2bc + 2ac}


⇒ 13{x2 + 4 – 4x + y2 + 1 + 2y} = 4{4x2 + 9y2 + 1 + 12xy – 6y – 4x}


⇒ 13x2 + 52 – 52x + 13y2 + 13 + 26y = 16x2 + 36y2 + 4 + 48xy – 24y – 16x


⇒ 13x2 + 52 – 52x + 13y2 + 13 + 26y – 16x2 – 36y2 – 4 – 48xy + 24y + 16x = 0


⇒ – 3x2 – 23y2 – 36x + 50y – 48xy + 61 = 0


3x2 + 23y2 + 36x – 50y + 48xy – 61 = 0


This is the required equation of hyperbola.



Question 7.

Find the equation of the hyperbola whose

focus is (a, 0), directrix is 2x + 3y = 1 and eccentricity = 2


Answer:

Given: Equation of directrix of a hyperbola is 2x – y + a = 0. Focus of hyperbola is (a, 0) and eccentricity (e) =


To find: equation of hyperbola


Let M be the point on directrix and P(x, y) be any point of hyperbola


Formula used:



where e is eccentricity, PM is perpendicular from any point P on hyperbola to the directrix


Therefore,




Squaring both sides:




{∵ (a – b)2 = a2 + b2 + 2ab &


(a + b + c)2 = a2 + b2 + c2 + 2ab + 2bc + 2ac}


⇒ 117{x2 + a2 – 2ax + y2} = 16{4x2 + y2 + a2 – 4xy – 2ay + 4ax}


⇒ 117x2 + 117a2 – 234ax + 117y2 = 64x2 + 16y2 + 16a2 – 64xy – 32ay + 64ax


⇒ 117x2 + 117a2 – 234ax + 117y2 – 64x2 – 16y2 – 16a2 + 64xy + 32ay – 64ax = 0


53x2 + 101y2 – 298ax + 32ay + 64xy + 111a2 = 0


This is the required equation of hyperbola.



Question 8.

Find the equation of the hyperbola whose

focus is (2, 2), directrix is x + y = 9 and eccentricity = 2


Answer:

Given: Equation of directrix of a hyperbola is x + y – 9 = 0. Focus of hyperbola is (2, 2) and eccentricity (e) = 2


To find: equation of hyperbola


Let M be the point on directrix and P(x, y) be any point of hyperbola


Formula used:



where e is eccentricity, PM is perpendicular from any point P on hyperbola to the directrix


Therefore,




Squaring both sides:




{∵ (a – b)2 = a2 + b2 + 2ab &


(a + b + c)2 = a2 + b2 + c2 + 2ab + 2bc + 2ac}


⇒ x2 + 4 – 4x + y2 + 4 – 4y = 2{x2 + y2 + 81 + 2xy – 18y – 18x}


⇒ x2 – 4x + y2 + 8 – 4y = 2x2 + 2y2 + 162 + 4xy – 36y – 36x


⇒ x2 – 4x + y2 + 8 – 4y – 2x2 – 2y2 – 162 – 4xy + 36y + 36x = 0


⇒ – x2 – y2 + 32x + 32y + 4xy – 154 = 0


x2 + y2 – 32x – 32y + 4xy + 154 = 0


This is the required equation of hyperbola.




Question 9.

Find the eccentricity, coordinates of the foci, equations of directrices and length of the latus-rectum of the hyperbola.

9x2 – 16y2 = 144


Answer:

Given: 9x2 – 16y2 = 144


To find: eccentricity(e), coordinates of the foci f(m,n), equation of directrix, length of latus-rectum of hyperbola.


9x2 – 16y2 = 144





Formula used:


For hyperbola


Eccentricity(e) is given by,



Foci is given by (±ae, 0)


Equation of directrix are:


Length of latus rectum is


Here, a = 4 and b = 3





⇒ c = 5


Therefore,




Foci: (±5, 0)


Equation of directrix are:







Length of latus rectum,






Question 10.

Find the eccentricity, coordinates of the foci, equations of directrices and length of the latus-rectum of the hyperbola.

16x2 – 9y2 = -144


Answer:

Given: 16x2 – 9y2 = -144


To find: eccentricity(e), coordinates of the foci f(m,n), equation of directrix, length of latus-rectum of hyperbola.





Formula used:


For hyperbola


Eccentricity(e) is given by,



Foci is given by (0, ±be)


The equation of directrix are:


Length of latus rectum is


Here, a = 3 and b = 4





⇒ c = 5


Therefore,




Foci: (0, ±5)


The equation of directrix are:







Length of latus rectum,






Question 11.

Find the eccentricity, coordinates of the foci, equations of directrices and length of the latus-rectum of the hyperbola.

4x2 – 3y2 = 36


Answer:

Given: 4x2 – 3y2 = 36


To find: eccentricity(e), coordinates of the foci f(m,n), equation of directrix, length of latus-rectum of hyperbola.





Formula used:


For hyperbola


Eccentricity(e) is given by,



Foci are given by (±ae, 0)


The equation of directrix are


Length of latus rectum is


Here, a = 3 and b =





Therefore,





The equation of directrix are:







Length of latus rectum,





= 8



Question 12.

Find the eccentricity, coordinates of the foci, equations of directrices and length of the latus-rectum of the hyperbola.

3x2 – y2 = 4


Answer:

Given: 3x2 – y2 = 4


To find: eccentricity(e), coordinates of the foci f(m,n), equation of directrix, length of latus-rectum of hyperbola.





Formula used:


For hyperbola


Eccentricity(e) is given by,



Foci are given by (±ae, 0)


The equation of directrix are


Length of latus rectum is


Here, a = and b = 2







Therefore,






The equation of directrix are:







Length of latus rectum,





Question 13.

Find the eccentricity, coordinates of the foci, equations of directrices and length of the latus-rectum of the hyperbola.

2x2 – 3y2 = 5


Answer:

Given: 2x2 – 3y2 = 5


To find: eccentricity(e), coordinates of the foci f(m,n), equation of directrix, length of latus-rectum of hyperbola.





Formula used:


For hyperbola


Eccentricity(e) is given by,



Foci are given by (±ae, 0)


The equation of directrix are


Length of latus rectum is


Here, a = and b =







Therefore,






The equation of directrix are:







Length of latus rectum,







Question 14.

Find the axes, eccentricity, latus-rectum and the coordinates of the foci of the hyperbola 25x2 – 36y2 = 225.


Answer:

Given: 2x2 – 3y2 = 5


To find: eccentricity(e), coordinates of the foci f(m,n), equation of directrix, length of latus-rectum of hyperbola.





Formula used:


For hyperbola


Eccentricity(e) is given by,



Foci are given by (±ae, 0)


The equation of directrix are


Length of latus rectum is


Here, a = 3 and b =







Therefore,






The equation of directrix are:







Length of latus rectum,







Question 15.

Find the centre, eccentricity, foci and directions of the hyperbola

16x2 – 9y2 + 32x + 36y – 164 = 0


Answer:

Given: 16x2 – 9y2 + 32x + 36y – 164 = 0


To find: center, eccentricity(e), coordinates of the foci f(m,n), equation of directrix.


16x2 – 9y2 + 32x + 36y – 164 = 0


⇒ 16x2 + 32x + 16 – 9y2 + 36y – 36 – 16 + 36 – 164 = 0


⇒ 16(x2 + 2x + 1) – 9(y2 – 4y + 4) – 16 + 36 – 164 = 0


⇒ 16(x2 + 2x + 1) – 9(y2 – 4y + 4) – 144 = 0


⇒ 16(x + 1)2 – 9(y – 2)2 = 144





Here, center of the hyperbola is (-1, 2)


Let x + 1 = X and y – 2 = Y



Formula used:


For hyperbola


Eccentricity(e) is given by,



Foci are given by (±ae, 0)


The equation of directrix are


Length of latus rectum is


Here, a = 3 and b = 4






Therefore,





⇒ X = ±5 and Y = 0


⇒ x + 1 = ±5 and y – 2 = 0


⇒ x = ±5 – 1 and y = 2


So, Foci: (±5 – 1, 2)


Equation of directrix are:












Question 16.

Find the centre, eccentricity, foci and directions of the hyperbola

x2 – y2 + 4x = 0


Answer:

Given: x2 – y2 + 4x = 0


To find: center, eccentricity(e), coordinates of the foci f(m,n), equation of directrix.


x2 – y2 + 4x = 0


⇒ x2 + 4x + 4 – y2 – 4 = 0


⇒ (x + 2)2 – y2 = 4




Here, center of the hyperbola is (2, 0)


Let x – 2 = X



Formula used:


For hyperbola


Eccentricity(e) is given by,



Foci are given by (±ae, 0)


The equation of directrix are


Length of latus rectum is


Here, a = 2 and b = 2






Therefore,






and y = 0


and y = 0


and y = 0



Equation of directrix are:










Question 17.

Find the centre, eccentricity, foci and directions of the hyperbola

x2 – 3y2 – 2x = 8


Answer:

Given: x2 – 3y2 – 2x = 8


To find: center, eccentricity(e), coordinates of the foci f(m,n), equation of directrix.


x2 – 3y2 – 2x = 8


⇒ x2 – 2x + 1 – 3y2 – 1 = 8


⇒ (x – 1)2 – 3y2 = 9




Here, center of the hyperbola is (1, 0)


Let x – 1 = X



Formula used:


For hyperbola


Eccentricity(e) is given by,



Foci is given by (±ae, 0)


Equation of directrix are:


Length of latus rectum is


Here, a = 3 and b =





Therefore,





and y = 0


and y = 0


and y = 0



Equation of directrix are:










Question 18.

Find the equation of the hyperbola, referred to its principal axes as axes of coordinates, in the following cases:

the distance between the foci = 16 and eccentricity =


Answer:

Given: the distance between the foci = 16 and eccentricity


To find: the equation of the hyperbola


Formula used:


For hyperbola:



Distance between the foci is 2ae and b2 = a2(e2 – 1)


Therefore


2ae = 16







b2 = a2(e2 – 1)





Equation of hyperbola is:




Hence, required equation of hyperbola is x2 – y2 = 32



Question 19.

Find the equation of the hyperbola, referred to its principal axes as axes of coordinates, in the following cases:

conjugate axis is 5 and the distance between foci = 13


Answer:

Given: the distance between the foci = 13 and conjugate axis is 5


To find: the equation of the hyperbola


Formula used:


For hyperbola:



Distance between the foci is 2ae and b2 = a2(e2 – 1)


Length of conjugate axis is 2b


Therefore




2ae = 13




b2 = a2(e2 – 1)


⇒ b2 = a2e2 – a2





Equation of hyperbola is:







Hence, required equation of hyperbola is 25x2 – 144y2 = 900



Question 20.

Find the equation of the hyperbola, referred to its principal axes as axes of coordinates, in the following cases:

conjugate axis is 7 and passes through the point (3, -2).


Answer:

Given: conjugate axis is 5 and passes through the point (3, -2)


To find: the equation of the hyperbola


Formula used:


For hyperbola:



Conjugate axis is 2b


Therefore




The equation of hyperbola is:



Since it passes through (3, -2)










The equation of hyperbola:








Hence, required equation of hyperbola is 65x2 – 36y2 = 441



Question 21.

Find the equation of the hyperbola whose

foci are (6, 4) and (-4, 4) and eccentricity is 2.


Answer:

Given: Foci are (6, 4) and (-4, 4) and eccentricity is 2


To find: equation of the hyperbola


Formula used:


The standard form of the equation of the hyperbola is,



Center is the mid-point of two foci.


Distance between the foci is 2ae and b2 = a2(e2 – 1)


The distancebetween two points (m, n) and (a, b) is given by


Mid-point theorem:


Mid-point of two points (m, n) and (a, b) is given by



Center of hyperbola having foci (6, 4) and (-4, 4) is given by




= (1, 4)


The distance between the foci is 2ae, and Foci are (6, 4) and (-4, 4)








{∵ e = 2}





b2 = a2(e2 – 1)






The equation of hyperbola:







⇒ 12(x2 + 1 – 2x) – 4(y2 + 16 – 8y) = 75


⇒ 12x2 + 12 – 24x – 4y2 – 64 + 32y – 75 = 0


⇒ 12x2 – 4y2 – 24x + 32y – 127 = 0


Hence, required equation of hyperbola is 12x2 – 4y2 – 24x + 32y – 127 = 0



Question 22.

Find the equation of the hyperbola whose

vertices are (-8, -1) and (16, -1) and focus is (17, -1)


Answer:

Given: Vertices are (-8, -1) and (16, -1) and focus is (17, -1)


To find: equation of the hyperbola


Formula used:


The standard form of the equation of the hyperbola is,



Center is the mid-point of two vertices


The distance between two vertices is 2a


The distance between the foci and vertex is ae – a and b2 = a2(e2 – 1)


The distancebetween two points (m, n) and (a, b) is given by


Mid-point theorem:


Mid-point of two points (m, n) and (a, b) is given by



Center of hyperbola having vertices (-8, -1) and (16, -1) is given by




= (4, -1)


The distance between two vertices is 2a and vertices are (-8, -1) and (16, -1)







The distance between the foci and vertex is ae – a, Foci is (17, -1) and the vertex is (16, -1)








b2 = a2(e2 – 1)







The equation of hyperbola:






⇒ 25(x2 + 16 – 8x) – 144(y2 + 1 + 2y) = 3600


⇒ 25x2 + 400 – 200x – 144y2 – 144 – 288y – 3600 = 0


⇒ 25x2 – 144y2 – 200x – 288y – 3344 = 0


Hence, required equation of hyperbola is 25x2 – 144y2 – 200x – 288y – 3344 = 0



Question 23.

Find the equation of the hyperbola whose

foci are (4, 2) and (8, 2) and eccentricity is 2.


Answer:

Given: Foci are (4, 2) and (8, 2) and eccentricity is 2


To find: equation of the hyperbola


Formula used:


The standard form of the equation of the hyperbola is,



Center is the mid-point of two foci.


Distance between the foci is 2ae and b2 = a2(e2 – 1)


The distancebetween two points (m, n) and (a, b) is given by


Mid-point theorem:


Mid-point of two points (m, n) and (a, b) is given by



Center of hyperbola having foci (4, 2) and (8, 2) is given by




= (6, 2)


The distance between the foci is 2ae and Foci are (4, 2) and (8, 2)








{∵ e = 2}





b2 = a2(e2 – 1)





The equation of hyperbola:







⇒ 3(x2 + 36 – 12x) – (y2 + 4 – 4y) = 3


⇒ 3x2 + 108 – 36x – y2 – 4 + 4y – 3 = 0


⇒ 3x2 – y2 – 36x + 4y + 101 = 0


Hence, required equation of hyperbola is 3x2 – y2 – 36x + 4y + 101 = 0



Question 24.

Find the equation of the hyperbola whose

vertices are at (0. ± 7) and foci at


Answer:

Given: Vertices are (0, ± 7) and foci are


To find: equation of the hyperbola


Formula used:


The standard form of the equation of the hyperbola is,



Vertices of the hyperbola are given by (0, ±b)


Foci of the hyperbola are given by (0, ±be)


Vertices are (0, ±7) and foci are


Therefore,





a2 = b2(e2 – 1)








The equation of hyperbola:






⇒ 9x2 – 7y2 = -343


⇒ 9x2 – 7y2 + 343 = 0


Hence, required equation of hyperbola is 9x2 – 7y2 + 343 = 0



Question 25.

Find the equation of the hyperbola whose

vertices are at (±6, 0) and one of the directrices is x = 4.


Answer:

Given: Vertices are (± 6, 0) and one of the directrices is x = 4


To find: equation of the hyperbola


Formula used:


The standard form of the equation of the hyperbola is,



Vertices of the hyperbola are given by (±a, 0)


The equation of the directrices:


Vertices are (± 6, 0) and one of the directrices is x = 4


Therefore,






b2 = a2(e2 – 1)







⇒ b2 = 45


The equation of hyperbola:





⇒ 5x2 – 4y2 = 180


⇒ 5x2 – 4y2 – 180 = 0


Hence, required equation of hyperbola is 5x2 – 4y2 – 180 = 0



Question 26.

Find the equation of the hyperbola whose

foci at (± 2, 0) and eccentricity is 3/2.


Answer:

Given: Foci are (2, 0) and (-2, 0) and eccentricity is


To find: equation of the hyperbola


Formula used:


The standard form of the equation of the hyperbola is,



Center is the mid-point of two foci.


Distance between the foci is 2ae and b2 = a2(e2 – 1)


The distancebetween two points (m, n) and (a, b) is given by


Mid-point theorem:


Mid-point of two points (m, n) and (a, b) is given by



Center of hyperbola having Foci (2, 0) and (-2, 0) is given by




= (0, 0)


The distance between the foci is 2ae, and Foci are (2, 0) and (-2, 0)












b2 = a2(e2 – 1)







The equation of hyperbola:







⇒ 45x2 – 36y2 – 80 = 0


Hence, required equation of hyperbola is 45x2 – 36y2 – 80 = 0



Question 27.

Find the eccentricity of the hyperbola, the length of whose conjugate axis is of the length of the transverse axis.


Answer:

Given: the length of whose conjugate axis is of the length of the transverse axis


To find: eccentricity of the hyperbola


Formula used:


The standard form of the equation of the hyperbola is,



Length of the conjugate axis is 2b and length of transverse axis is 2a


According to question:





We know,







Hence, the eccentricity of the hyperbola is



Question 28.

Find the equation of the hyperbola whose

the focus is at (5, 2), vertices at (4, 2) and (2, 2) and centre at (3, 2)


Answer:

Given: Vertices are (4, 2) and (2, 2), the focus is (5, 2) and centre (3, 2)


To find: equation of the hyperbola


Formula used:


The standard form of the equation of the hyperbola is,



Center is the mid-point of two vertices


The distance between two vertices is 2a


The distance between the foci and vertex is ae – a and b2 = a2(e2 – 1)


The distancebetween two points (m, n) and (a, b) is given by


Mid-point theorem:


Mid-point of two points (m, n) and (a, b) is given by



The distance between two vertices is 2a and vertices are (4, 2) and (2, 2)







The distance between the foci and vertex is ae – a, Foci is (5, 2) and the vertex is (4, 2)





⇒ 1 = e – 1


⇒ e = 1 + 1


⇒ e = 2


b2 = a2(e2 – 1)







The equation of hyperbola:



{∵ Centre (3, 2)}





⇒ 3(x2 + 9 – 6x) – (y2 + 4 – 4y) = 3


⇒ 3x2 + 27 – 18x – y2 – 4 + 4y – 3 = 0


⇒ 3x2 – y2 – 18x + 4y + 20 = 0


Hence, required equation of hyperbola is 3x2 – y2 – 18x + 4y + 20 = 0



Question 29.

Find the equation of the hyperbola whose

focus is at (4, 2), centre at (6, 2) and e = 2.


Answer:

Given: Foci is (4, 2), e = 2 and center at (6, 2)


To find: equation of the hyperbola


Formula used:


The standard form of the equation of the hyperbola is,



Center is the mid-point of two vertices


The distance between two vertices is 2a


The distance between the foci and vertex is ae – a and b2 = a2(e2 – 1)


The distancebetween two points (m, n) and (a, b) is given by


Mid-point theorem:


Mid-point of two points (m, n) and (a, b) is given by



Therefore


Let one of the two foci is (m, n) and the other one is (4, 2)


Since, Centre(6, 2)





Foci are (4, 2) and (8, 2)


The distance between the foci is 2ae and Foci are (4, 2) and (8, 2)











⇒ a2 = 1


b2 = a2(e2 – 1)



⇒ b2 = 4 – 1


⇒ b2 = 3


The equation of hyperbola:





⇒ 3(x2 + 36 – 12x) – (y2 + 4 – 4y) = 3


⇒ 3x2 + 108 – 36x – y2 – 4 + 4y – 3 = 0


⇒ 3x2 – y2 – 36x + 4y + 101 = 0


Hence, required equation of hyperbola is 3x2 – y2 – 36x + 4y + 101 = 0



Question 30.

If P is any point on the hyperbola whose axis are equal, prove that SP.S’P = CP2


Answer:

Given: Axis of the hyperbola are equal, i.e. a = b


To prove: SP.S’P = CP2


Formula used:


The standard form of the equation of the hyperbola is,







Foci of the hyperbola are given by (±ae, 0)




Let P (m, n) be any point on the hyperbola


The distancebetween two points (m, n) and (a, b) is given by






C is Centre with coordinates (0, 0)





Now,







{∵ a2 = m2 – n2}





From (i):



Taking square root both sides:




Hence Proved



Question 31.

In each of the following find the equations of the hyperbola satisfying the given conditions

vertices (± 2, 0), foci (± 3, 0)


Answer:

Given: Vertices are (±2, 0) and foci are (±3, 0)


To find: equation of the hyperbola


Formula used:


The standard form of the equation of the hyperbola is,



Vertices of the hyperbola are given by (±a, 0)


Foci of the hyperbola are given by (±ae, 0)


Vertices are (±2, 0) and foci are (±3, 0)


Therefore,


a = 2 and ae = 3


⇒ 2 × e = 3



b2 = a2(e2 – 1)







⇒ b2 = 5


The equation of hyperbola:





⇒ 5x2 – 4y2 = 20


⇒ 5x2 – 4y2 – 20 = 0


Hence, required equation of hyperbola is 5x2 – 4y2 – 20 = 0



Question 32.

In each of the following find the equations of the hyperbola satisfying the given conditions

vertices (0, ± 5), foci (0, ± 8)


Answer:

Given: Vertices are (0, ±5) and foci are (0, ±8)


To find: equation of the hyperbola


Formula used:


The standard form of the equation of the hyperbola is,



Vertices of the hyperbola are given by (0, ±b)


Foci of the hyperbola are given by (0, ±be)


Vertices are (0, ±5) and foci are (0, ±8)


Therefore,





a2 = b2(e2 – 1)







⇒ a2 = 39


The equation of hyperbola:




Hence, the required equation of the hyperbola is



Question 33.

In each of the following find the equations of the hyperbola satisfying the given conditions

vertices (0, ± 3), foci (0, ± 5)


Answer:

Given: Vertices are (0, ±3) and foci are (0, ±5)


To find: equation of the hyperbola


Formula used:


The standard form of the equation of the hyperbola is,



Vertices of the hyperbola are given by (0, ±b)


Foci of the hyperbola are given by (0, ±be)


Vertices are (0, ±3) and foci are (0, ±5)


Therefore,





a2 = b2(e2 – 1)







⇒ a2 = 16


The equation of hyperbola:




Hence, the required equation of the hyperbola is



Question 34.

In each of the following find the equations of the hyperbola satisfying the given conditions

foci (±5, 0), transverse axis = 8


Answer:

To find: equation of the hyperbola


Formula used:


The standard form of the equation of the hyperbola is,



Length of transverse axis is 2a


Coordinates of the foci for a standard hyperbola is given by (±ae, 0)


According to question:


2a = 8 and ae = 5


2a = 8



⇒ a = 4


⇒ a2 = 16


ae = 5




We know,


b2 = a2(e2 – 1)






⇒ b2 = 4(21)


⇒ b2 = 84


Hence, the equation of the hyperbola is:





Question 35.

In each of the following find the equations of the hyperbola satisfying the given conditions

foci (0, ±13), conjugate axis = 24


Answer:

Given: foci (0, ±13) and the conjugate axis is 24


To find: equation of the hyperbola


Formula used:


The standard form of the equation of the hyperbola is,



Length of the conjugate axis is 2b


Coordinates of the foci for a standard hyperbola is given by (0, ±be)


According to question:


2b = 24 and be = 13


2b = 24



⇒ b = 12


⇒ b2 = 144


be = 12




We know,


a2 = b2(e2 – 1)






⇒ b2 = 25


Hence, the equation of the hyperbola is:





Question 36.

In each of the following find the equations of the hyperbola satisfying the given conditions

foci , the latus-rectum = 8


Answer:

Given: Foci and the latus-rectum = 8


To find: equation of the hyperbola


Formula used:


The standard form of the equation of the hyperbola is,



Coordinates of the foci for a standard hyperbola is given by (±ae, 0)


Length of latus rectum is


According to the question:










We know,


b2 = a2(e2 – 1)




⇒ 4a = 45 – a2


⇒ a2 + 4a – 45 = 0


⇒ a2 + 9a – 5a – 45 = 0


⇒ a(a + 9) – 5(a + 9) = 0


⇒ (a + 9)(a – 5) = 0


⇒ a = -9 or a = 5


Since a is a distance, and it can’t be negative


⇒ a = 5


⇒ a2 = 25


b2 = 4a


⇒ b2 = 4(5)


⇒ b2 = 20


Hence, equation of hyperbola is:





Question 37.

In each of the following find the equations of the hyperbola satisfying the given conditions

foci (±4, 0), the latus-rectum = 12


Answer:

Given: Foci (±4, 0), the latus-rectum = 12


To find: equation of the hyperbola


Formula used:


Standard form of the equation of hyperbola is,



Coordinates of the foci for a standard hyperbola is given by (±ae, 0)


Length of latus rectum is


According to the question:



ae = 4








We know,


b2 = a2(e2 – 1)




⇒ 6a = 16 – a2


⇒ a2 + 6a – 16 = 0


⇒ a2 + 8a – 2a – 16 = 0


⇒ a(a + 8) – 2(a + 8) = 0


⇒ (a + 8)(a – 2) = 0


⇒ a = -8 or a = 2


Since a is a distance, and it can’t be negative,


⇒ a = 2


⇒ a2 = 4


b2 = 6a


⇒ b2 = 6(2)


⇒ b2 = 12


Hence, equation of hyperbola is:





Question 38.

In each of the following find the equations of the hyperbola satisfying the given conditions

foci , passing through (2, 3)


Answer:

Given: passing through (2, 3)


To find: equation of the hyperbola


Formula used:


The standard form of the equation of the hyperbola is,



Coordinates of the foci for a standard hyperbola is given by (0, ±be)


According to the question:



⇒ b2e2 = 10


Since (2, 3) passing through hyperbola


Therefore,





{∵ a2 = b2(e2 – 1)}








⇒ 90 – 13b2 = (10 – b2)b2


⇒ 90 – 13b2 = 10b2 – b4


⇒ 90 – 13b2 – 10b2 + b4 = 0


⇒ b4 – 23b2 + 90 = 0


⇒ b4 – 18b2 – 5b2 + 90 = 0


⇒ b2(b2 – 18) – 5(b2 – 18) = 0


⇒ (b2 – 18)(b2 – 5) = 0


⇒ b2 = 18 or 5


Case 1: b2 = 18 and b2e2 = 10


a2 = b2(e2 – 1)


⇒ a2 = b2e2 – b2


⇒ a2 = 10 – 18


⇒ a2 = – 8


Hence, equation of hyperbola is:






Case 2: b2 = 5 and b2e2 = 10


a2 = b2(e2 – 1)


⇒ a2 = b2e2 – b2


⇒ a2 = 10 – 5


⇒ a2 = 5


Hence, equation of hyperbola is:





Question 39.

In each of the following find the equations of the hyperbola satisfying the given conditions

foci (0, ± 12), latus-rectum = 36.


Answer:

Given: Foci (0, ±12), the latus-rectum = 36


To find: equation of the hyperbola


Formula used:


The standard form of the equation of the hyperbola is,



Coordinates of the foci for a standard hyperbola is given by (0, ±be)


Length of latus rectum is


According to the question:



be = 12








We know,


a2 = b2(e2 – 1)




⇒ 18b = 144 – b2


⇒ b2 + 18b – 144 = 0


⇒ b2 + 24b – 6b – 144 = 0


⇒ b(b + 24) – 6(b + 24) = 0


⇒ (b + 24)(b – 6) = 0


⇒ b = -24 or b = 6


Since b is a distance, and it can’t be negative


⇒ b = 6


⇒ b2 = 36


a2 = 18b


⇒ a2 = 18(6)


⇒ b2 = 108


Hence, equation of hyperbola is:





Question 40.

If the distance between the foci of a hyperbola is 16 and its eccentricity is, then obtain its equation.


Answer:

Given: Distance between foci is 16 and eccentricity is


To find: equation of the hyperbola


Formula used:


The standard form of the equation of the hyperbola is,



The distance between foci is given by 2ae


According to question:


2ae = 16






⇒ a2 = 32


We know,


b2 = a2(e2 – 1)




⇒ b2 = 32


Hence, the equation of the hyperbola is:




x2 – y2 = 32



Question 41.

Show that the set of all points such that the difference of their distances from (4, 0) and (-4, 0) is always equal to 2 represents a hyperbola.


Answer:

To prove: the set of all points under given conditions represents a hyperbola


Let a point P be (x, y) such that the difference of their distances from (4, 0) and (-4, 0) is always equal to 2.


Formula used:


The distance between two points (m, n) and (a, b) is given by



The distance of P(x, y) from (4, 0) is


The distance of P(x, y) from (-4, 0) is


Since, the difference of their distances from (4, 0) and (-4, 0) is always equal to 2


Therefore,




Squaring both sides:










Squaring both sides:



⇒ 16x2 + 1 – 8x = (x – 4)2 + y2


⇒ 16x2 + 1 – 8x = x2 + 16 – 8x + y2


⇒ 16x2 + 1 – 8x – x2 – 16 + 8x – y2 = 0


⇒ 15x2 – y2 – 15 = 0


Hence, required equation of hyperbola is 15x2 – y2 – 15 = 0




Very Short Answer
Question 1.

Write the eccentricity of the hyperbola 9x2 – 16y2 = 144.


Answer:

Given: 9x2 – 16y2 = 144


To find: eccentricity(e)


9x2 – 16y2 = 144





Formula used:


For hyperbola


Eccentricity(e) is given by,



Here, a = 4 and b = 3





⇒ c = 5


Therefore,



Hence, eccentricity is



Question 2.

Write the eccentricity of the hyperbola whose latus-rectum is half of its transverse axis.


Answer:

Given: Latus-rectum is half of its transverse axis


To find: eccentricity of the hyperbola


Formula used:


Standard form of the equation of hyperbola is,



Length of transverse axis is 2a


Latus-rectum of the hyperbola is


According to question:


Latus-rectum is half of its transverse axis




We know,







Hence, eccentricity is



Question 3.

Write the coordinates of the foci of the hyperbola 9x2 – 16y2 = 144.


Answer:

Given: 9x2 – 16y2 = 144


To find: coordinates of the foci f(m,n)


9x2 – 16y2 = 144





Formula used:


For hyperbola


Eccentricity(e) is given by,



Foci is given by (±ae, 0)


Here, a = 4 and b = 3





⇒ c = 5


Therefore,




Foci: (±5, 0)



Question 4.

Write the equation of the hyperbola of eccentricity, if it is known that the distance between its foci is 16.


Answer:

Given: Distance between foci is 16 and eccentricity is


To find: equation of the hyperbola


Formula used:


Standard form of the equation of hyperbola is,



Distance between foci is given by 2ae


According to question:


2ae = 16






⇒ a2 = 32


We know,


b2 = a2(e2 – 1)




⇒ b2 = 32


Hence, equation of hyperbola is:




x2 – y2 = 32



Question 5.

If the foci of the ellipse and the hyperbola coincide, write the value of b2


Answer:

To find: value of b2


Given: foci of given ellipse and hyperbola coincide







Formula used:


Coordinates of the foci for standard ellipse is given by (±c1, 0) where


Coordinates of the foci for standard hyperbola is given by (±c2, 0) where


Since, their foci coincide




Here a1 = 4, b1 = b,






⇒ b2 = 16 – 9


b2 = 7



Question 6.

Write the length of the latus-rectum of the hyperbola 16x2 – 9y2 = 144.


Answer:

Given: 16x2 – 9y2 = 144


To find: length of latus-rectum of hyperbola.


16x2 – 9y2 = 144





Formula used:


For hyperbola


Length of latus rectum is


Here, a = 3 and b = 4


Length of latus rectum,






Question 7.

If the latus-rectum through one focus of a hyperbola subtends a right angle at the farther vertex, then write the eccentricity of the hyperbola.


Answer:

Given: latus-rectum through one focus of a hyperbola subtends a right angle at the farther vertex


To find: eccentricity of hyperbola


Let B is vertex of hyperbola and A and C are point of intersection of latus-rectum and hyperbola



Standard equation of hyperbola is



Since, A and C lie on hyperbola


Therefore







As angle between AB and AC is 90°


⇒ SlopeAB × SlopeBC = -1





From (i):




{∵ b2 = a2(e2 – 1)}



⇒ (e2 – 1)2 = (e + 1)2


⇒ e4 + 1 – 2e2 = e2 + 1 + 2e


⇒ e4 + 1 – 2e2 – e2 – 1 – 2e = 0


⇒ e4 – 3e2 – 2e = 0


⇒ e(e3 – 3e – 2) = 0


⇒ e(e– 2)(e + 1)2 = 0


⇒ e = 0 or 2 or -1


But e should be greater than or equal to 1 for hyperbola


⇒ e = 2


Hence, eccentricity of hyperbola is 2



Question 8.

Write the distance between the directrices of the hyperbola

x = 8 sec θ, y = 8 tan θ.


Answer:

Given: Hyperbola is x = 8 sec θ and y = 8 tan θ


To find: equation of the hyperbola


Formula used:


Standard form of the equation of hyperbola is,



Distance between directrix is given by


x = 8 sec θ and y = 8 tan θ



We know,


sec2 θ – tan2 θ = 1




Here a = 8 and b = 8


Now,






Hence, distance between directrix,






Question 9.

Write the equation of the hyperbola whose vertices are (±3, 0) and foci at (±5, 0).


Answer:

Given: Vertices are (±3, 0) and foci are (±5, 0)


To find: equation of the hyperbola


Formula used:


Standard form of the equation of hyperbola is,



Vertices of hyperbola are given by (±a, 0)


Foci of hyperbola are given by (±ae, 0)


Vertices are (±3, 0) and foci are (±5, 0)


Therefore,


a = 3 and ae = 5


⇒ 3 × e = 5



b2 = a2(e2 – 1)







⇒ b2 = 16


Equation of hyperbola:




Hence, required equation of hyperbola is



Question 10.

If e1 and e2 are respectively the eccentricities of the ellipse and the hyperbola , then write the value of 2e12 + e22.


Answer:

Given: e1 and e2 are respectively the eccentricities of the ellipse and the hyperbola


To find: value of 2e12 + e22




Eccentricity(e) of hyperbola is given by,



Here a = 3 and b = 2





Therefore,



For ellipse:




Eccentricity(e) of ellipse is given by,







Therefore,





Substituting values from (1) and (2) in 2e12 + e22


2e12 + e22







= 3


Hence, value of 2e12 + e22 is 3




Mcq
Question 1.

Equation of the hyperbola whose vertices are (± 3, 0) and foci at (± 5, 0), is
A. 16x2 – 9y2 = 144

B. 9x2 – 16y2 = 144

C. 25x2 – 9y2 = 225

D. 9x2 – 25y2 = 81


Answer:

Given: Vertices are (±3, 0) and foci are (±5, 0)


To find: equation of the hyperbola


Formula used:


Standard form of the equation of hyperbola is,



Vertices of hyperbola are given by (±a, 0)


Foci of hyperbola are given by (±ae, 0)


Vertices are (±3, 0) and foci are (±5, 0)


Therefore,


a = 3 and ae = 5


⇒ 3 × e = 5



b2 = a2(e2 – 1)







⇒ b2 = 16


Equation of hyperbola:





⇒ 16x2 – 9y2 = 144


Hence, required equation of hyperbola is 16x2 – 9y2 = 144


Question 2.

If e1 and e2 are respectively the eccentricities of the ellipse and the hyperbola , then the relation between e1 and e2 is
A. 3e12 + e22 = 2

B. e12 + 2e22 = 3

C. 2e12 + e22 = 3

D. e12 + 3e22 = 2


Answer:

Given: e1 and e2 are respectively the eccentricities of the ellipse and the hyperbola


To find: value of 2e12 + e22




Eccentricity(e) of hyperbola is given by,



Here a = 3 and b = 2





Therefore,



For ellipse:




Eccentricity(e) of ellipse is given by,







Therefore,





Substituting values from (1) and (2) in 2e12 + e22


2e12 + e22







= 3


Hence, value of 2e12 + e22 is 3


Question 3.

The distance between the directrices of the hyperbola x = 8 sec θ, y = 8 tan θ, is
A.

B.

C.

D.


Answer:

Given: Hyperbola is x = 8 sec θ and y = 8 tan θ


To find: equation of the hyperbola


Formula used:


Standard form of the equation of hyperbola is,



Distance between directrix is given by


x = 8 sec θ and y = 8 tan θ



We know,


sec2 θ – tan2 θ = 1




Here a = 8 and b = 8


Now,






Hence, distance between directrix,





Question 4.

The equation of the conic with focus at (1, -1) directrix along x – y + 1= 0 and eccentricity is
A. xy = 1

B. 2xy + 4x – 4y – 1 = 0

C. x2 – y2 = 1

D. 2xy – 4x + 4y + 1 = 0


Answer:

Given: Equation of directrix of a hyperbola is x – y + 1= 0. Focus of hyperbola is (1, -1) and eccentricity (e) is


To find: equation of conic


Let M be the point on directrix and P(x, y) be any point of hyperbola


Formula used:



where e is eccentricity, PM is perpendicular from any point P on hyperbola to the directrix


Therefore,




Squaring both sides:





{∵ (a – b)2 = a2 + b2 + 2ab}


⇒ x2 + 1 – 2x + y2 + 1 + 2y = x2 + y2 + 1 – 2xy + 2x – 2y


⇒ x2 + 1 – 2x + y2 + 1 + 2y – x2 – y2 + 2xy – 1 – 2x + 2y = 0


2xy – 4x + 4y + 1 = 0


This is the required equation of hyperbola


Question 5.

The eccentricity of the conic 9x2 – 16y2 = 144 is
A.

B.

C.

D.


Answer:

Given: 9x2 – 16y2 = 144


To find: eccentricity(e)


9x2 – 16y2 = 144





Formula used:


For hyperbola


Eccentricity(e) is given by,



Here, a = 4 and b = 3





⇒ c = 5


Therefore,



Hence, eccentricity is


Question 6.

The latus-rectum of the hyperbola 16x2 – 9y2 = 144 is
A. 16/3

B. 32/3

C. 8/3

D. 4/3


Answer:

Given: 16x2 – 9y2 = 144


To find: length of latus-rectum of hyperbola.


16x2 – 9y2 = 144





Formula used:


For hyperbola


Length of latus rectum is


Here, a = 3 and b = 4


Length of latus rectum,





Question 7.

A point moves in a plane so that its distances PA and PB from two fixed points A and B in the plane satisfy the relation PA – PB = k(k ≠ 0), then the locus of P is
A. a hyperbola

B. a branch of the hyperbola

C. a parabola

D. an ellipse


Answer:

We know it by the fact that when difference in distances is constant, it forms as hyperbola


Question 8.

The eccentricity of the hyperbola whose latus-rectum is half of its transverse axis, is
A.

B.

C.

D. none of these


Answer:

Given: Latus-rectum is half of its transverse axis


To find: eccentricity of the hyperbola


Formula used:


Standard form of the equation of hyperbola is,



Length of transverse axis is 2a


Latus-rectum of the hyperbola is


According to question:


Latus-rectum is half of its transverse axis




We know,







Hence, eccentricity is


Question 9.

The eccentricity of the hyperbola x2 – 4y2 = 1 is
A.

B.

C.

D.


Answer:

Given: x2 – 4y2 = 1


To find: eccentricity(e)


x2 – 4y2 = 1




Formula used:


For hyperbola


Eccentricity(e) is given by,



Here, a = 1 and






Therefore,




Hence, eccentricity is


Question 10.

The difference of the focal distances of any point on the hyperbola is equal to
A. length of the conjugate axis

B. eccentricity

C. length of the transverse axis

D. Latus-rectum



Answer:

This is definition of eccentricity.


Eccentricity is difference of the focal distances of any point on the hyperbola


Question 11.

the foci of the hyperbola 9x2 – 16y2 = 144 are
A. (± 4, 0)

B. (0, ± 4)

C. (± 5, 0)

D. (0, ± 5)


Answer:

Given: 9x2 – 16y2 = 144


To find: coordinates of the foci f(m,n)


9x2 – 16y2 = 144





Formula used:


For hyperbola


Eccentricity(e) is given by,



Foci is given by (±ae, 0)


Here, a = 4 and b = 3





⇒ c = 5


Therefore,




Foci: (±5, 0)


Question 12.

The distance between the foci of a hyperbola is 16 and its eccentricity is , then equation of the hyperbola is
A. x2 + y2 = 32

B. x2 – y2 = 16

C. x2 + y2 = 16

D. x2 – y2 = 32


Answer:

Given: Distance between foci is 16 and eccentricity is


To find: equation of the hyperbola


Formula used:


Standard form of the equation of hyperbola is,



Distance between foci is given by 2ae


According to question:


2ae = 16






⇒ a2 = 32


We know,


b2 = a2(e2 – 1)




⇒ b2 = 32


Hence, equation of hyperbola is:




x2 – y2 = 32


Question 13.

If e1 is the eccentricity of the conic 9x2 + 4y2 = 36 and e2 is the eccentricity of the conic 9x2 – 4y2 = 36, then
A. e12 – e22 = 2

B. 2 < e22 – e12< 3

C. e22 – e12 = 2

D. e22 – e12> 3


Answer:

Given: e1 and e2 are respectively the eccentricities of 9x2 + 4y2 = 36 and 9x2 – 4y2 = 36 respectively


To find: e12 – e22


9x2 – 4y2 = 36





Eccentricity(e) of hyperbola is given by,



Here a = 2 and b = 3





Therefore,



For ellipse:


9x2 + 4y2 = 36





Eccentricity(e) of ellipse is given by,



Here a = 2 and b = 3





Therefore,



Substituting values from (1) and (2) in 2e12 + e22


e12 – e22






⇒ e22 – e22



Hence, value of 2 < e22 – e12 < 3


Question 14.

If the eccentricity of the hyperbola x2 – y2 sec2∝ = 5 is times the eccentricity of the ellipse x2 sec2∝ +y2 = 25, then ∝ =
A.

B.

C.

D.


Answer:

Given: e1 and e2 are respectively the eccentricities of x2 – y2 sec2 α = 5 and x2 sec2 α + y2 = 25 respectively


To find: value of α


x2 – y2 sec2 α = 5





Eccentricity(e) of hyperbola is given by,











Therefore,




For ellipse:


x2 sec2 α + y2 = 25






Eccentricity(e) of ellipse is given by,








Therefore,




According to question:


Eccentricity of given hyperbola is time eccentricity of given ellipse



From (1) and (2):



Squaring both sides:


⇒ 1 + cos2 α = 3(1 – cos2 α)


⇒ 1 + cos2 α = 3 – 3 cos2 α


⇒ 3 cos2 α + cos2 α = 3 – 1


⇒ 4 cos2 α = 2





Question 15.

The equation of the hyperbola whose foci are (6, 4) and (-4, 4) and eccentricity 2, is
A.

B.

C.

D. none of these


Answer:

Given: Foci are (6, 4) and (-4, 4) and eccentricity is 2


To find: equation of the hyperbola


Formula used:


Standard form of the equation of hyperbola is,



Center is the mid-point of two foci.


Distance between the foci is 2ae and b2 = a2(e2 – 1)


Distance between two points (m, n) and (a, b) is given by



Mid-point theorem:


Mid-point of two points (m, n) and (a, b) is given by



Center of hyperbola having foci (6, 4) and (-4, 4) is given by




= (1, 4)


Distance between the foci is 2ae and Foci are (6, 4) and (-4, 4)








{∵ e = 2}





b2 = a2(e2 – 1)






Equation of hyperbola:




Hence, required equation of hyperbola is


Question 16.

The length of the straight line x – 3y = 1 intercepted by the hyperbola x2 – 4y2 = 1 is
A.

B.

C.

D. none of these


Answer:

Given: A straight line x – 3y = 1 intercepts hyperbola x2 – 4y2 = 1


To find: Length of the intercepted line


Formula used:


Distance between two points (m, n) and (a, b) is given by



Firstly we will find point of intersections of given line and hyperbola


x – 3y = 1 ⇒ x = 1 + 3y


x2 – 4y2 = 1


⇒ (1 + 3y)2 – 4y2 = 1


⇒ 1 + 9y2 + 6y – 4y2 = 1


⇒ 5y2 + 6y = 0


⇒ y(5y + 6) = 0


⇒ y = 0 or 5y + 6 = 0



Now, x = 1 + 3y





So, Point of intersections are A(1, 0) and



Distance between point of intersections is









Question 17.

The foci of the hyperbola 2x2 – 3y2 = 5 are
A.

B. (± 5/6, 0)

C.

D. none of these


Answer:

Given: 2x2 – 3y2 = 5


To find: coordinates of the foci f(m,n)


2x2 – 3y2 = 5





Formula used:


For hyperbola


Eccentricity(e) is given by,



Foci is given by (±ae, 0)








Therefore,






Question 18.

The eccentricity the hyperbola is
A.

B.

C.

D.


Answer:

Given: Equation of hyperbola


To find:Eccentricity of the hyperbola




Squaring both sides:








Squaring both sides:






From (1) and (2):





Formula used:


For hyperbola


Eccentricity(e) is given by,



Here a = a, b = a





Therefore,




Hence, theeccentricity of the hyperbola is


Question 19.

The equation of the hyperbola whose centre is (6, 2) one focus is (4, 2) and of eccentricity 2 is
A. 3 (x – 6)2 – (y – 2)2 = 3

B. (x – 6)2 – 3 (y – 2)2 = 1

C. (x – 6)2 – 2(y – 2)2 = 1

D. 2(x – 6)2 – (y – 2)2 = 1


Answer:

Given: Foci is (4, 2), e = 2 and center at (6, 2)


To find: equation of the hyperbola


Formula used:


Standard form of the equation of hyperbola is,



Center is the mid-point of two vertices


The distance between two vertices is 2a


The distance between the foci and vertex is ae – a and b2 = a2(e2 – 1)


The distancebetween two points (m, n) and (a, b) is given by



Mid-point theorem:


Mid-point of two points (m, n) and (a, b) is given by



Therefore


Let one of the two foci is (m, n) and the other one is (4, 2)


Since, Centre(6, 2)





Foci are (4, 2) and (8, 2)


The distance between the foci is 2ae and Foci are (4, 2) and (8, 2)











⇒ a2 = 1


b2 = a2(e2 – 1)



⇒ b2 = 4 – 1


⇒ b2 = 3


Equation of hyperbola:





3(x – 6)2 – (y – 2)2 = 3


Hence, required equation of hyperbola is 3(x – 6)2 – (y – 2)2 = 3


Question 20.

The locus of the point of intersection of the lines and is a hyperbola of eccentricity
A. 1

B. 2

C. 3

D. 4


Answer:

Given: A hyperbola is formed by the locus of the point of intersection of lines


To find: Eccentricity of the hyperbola




Multiply by λ:



Adding (1) and (2):









Now, From (1):











Squaring both sides:









From (3) and (4):






Formula used:


For hyperbola


Eccentricity(e) is given by,







⇒ c = 8


Therefore,



⇒ e = 2


Hence, eccentricity of hyperbola is 2