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Differential Equations And Their Formation

Class 12th Mathematics RS Aggarwal Solution
Exercise 18a
  1. {d^{4}y}/{ dx^{4} } - cos ( frac {d^{3}y}/{ dx^{3} } ) = 0 Write order and…
  2. ( {dy}/{dx} ) ^{4} + 3y ( frac {d^{2}y}/{ dx^{2} } ) = 0 Write order and…
  3. x^{3} ( {d^{2}y}/{ dx^{2} } ) ^{2} + x ( frac {dy}/{dx} ) ^{4} = 0 Write…
  4. ( {d^{2}s}/{ dt^{2} } ) ^{2} + ( frac {ds}/{dt} ) ^{3} + 4 = 0 Write order…
  5. ( {d^{3}y}/{ dx^{3} } ) ^{2} + ( frac {d^{2}y}/{ dx^{2} } ) ^{3} + ( frac…
  6. {d^{2}y}/{ dx^{2} } + ( frac {dy}/{dx} ) ^{2} + 2y = 0 Write order and degree…
  7. {dy}/{dx} + y = e^{x} Write order and degree (if defined)of each of the…
  8. {d^{2}y}/{ dx^{2} } + y^{2} + e^ { (dy/dx) } = 0 Write order and degree (if…
  9. {dy}/{dx} + sin ( frac {dy}/{dx} ) = 0 Write order and degree (if defined)of…
  10. {d^{2}y}/{ dx^{2} } + 5x ( frac {dy}/{dx} ) ^{2} - 6y = logx Write order and…
  11. ( {dy}/{dx} ) ^{3} - 4 ( frac {dy}/{dx} ) ^{2} + 7y = sinx Write order and…
  12. {d^{3}y}/{ dx^{3} } + 2 frac {d^{2}y}/{ dx^{2} } + frac {dy}/{dx} = 0 Write…
  13. x ( {dy}/{dx} ) + frac {2}/{ ( frac {dy}/{dx} ) } + 9 = y^{2} Write order…
  14. root { 1 - ( {dy}/{dx} ) ^{2} } = ( a frac {d^{2}y}/{ dx^{2} } ) ^{1/3}…
  15. root { 1-y^{2} } dx + sqrt { 1-x^{2} } dy = 0 Write order and degree (if…
  16. ( y^ { there eξ sts prime } ) ^{3} + ( y^ { prime } ) ^{2} + siny^ { prime }…
  17. (3x + 5y)dy - 4x2 dx = 0 Write order and degree (if defined)of each of the…
  18. y = {dy}/{dx} + frac {5}/{ ( frac {dy}/{dx} ) } Write order and degree (if…
Exercise 18b
  1. Verify that x2 = 2y2log y is a solution of the differential equation (x2 + y2)…
  2. Verify that x2 = 2y2log y is a solution of the differential equation (x2 + y2)…
  3. Verify that y = ex cos bx is a solution of the differential equation…
  4. Verify that y = ex cos bx is a solution of the differential equation…
  5. Verify that y = e^{mcos^{-1}x} is a solution of the differential equation (1…
  6. Verify that y = e^{mcos^{-1}x} is a solution of the differential equation (1…
  7. Verify that y = (a + bx) e2x is the general solution of the differential…
  8. Verify that y = (a + bx) e2x is the general solution of the differential…
  9. Verify that y = ex(A cos x + B sin x) is the general solution of the…
  10. Verify that y = ex(A cos x + B sin x) is the general solution of the…
  11. Verify that y = A cos 2x - B sin 2x is the general solution of the differential…
  12. Verify that y = A cos 2x - B sin 2x is the general solution of the differential…
  13. Verify that y = ae2x + be - x is the general solution of the differential…
  14. Verify that y = ae2x + be - x is the general solution of the differential…
  15. Show that y = ex(A cos x + B sin x) is the solution of the differential…
  16. Show that y = ex(A cos x + B sin x) is the solution of the differential…
  17. Verify that y2 = 4a(x + a) is a solution of the differential equation y { 1 -…
  18. Verify that y2 = 4a(x + a) is a solution of the differential equation y { 1 -…
  19. Verify that y = ce^{tan^{-1}x} is a solution of the differential equation (1…
  20. Verify that y = ce^{tan^{-1}x} is a solution of the differential equation (1…
  21. Verify that y = ae^{bx} is a solution of the differential equation…
  22. Verify that y = ae^{bx} is a solution of the differential equation…
  23. Verify that y = {a}/{x} + b is a solution of the differential equation…
  24. Verify that y = {a}/{x} + b is a solution of the differential equation…
  25. Verify that y = e - x + Ax + B is a solution of the differential equation…
  26. Verify that y = e - x + Ax + B is a solution of the differential equation…
  27. Verify that Ax2 + By2 = 1 is a solution of the differential equation x { y…
  28. Verify that Ax2 + By2 = 1 is a solution of the differential equation x { y…
  29. Verify that y = {c-x}/{1+cx} is a solution of the differential equation…
  30. Verify that y = {c-x}/{1+cx} is a solution of the differential equation…
  31. Verify that y = log (x + root { x^{2} + a^{2} } ) satisfies the…
  32. Verify that y = log (x + root { x^{2} + a^{2} } ) satisfies the…
  33. Verify that y = e - 3x is a solution of the differential equation…
  34. Verify that y = e - 3x is a solution of the differential equation…
Exercise 18c
  1. Form the differential equation of the family of straight lines y=mx+c, where m…
  2. Form the differential equation of the family of concentric circles x2+y2=a2,…
  3. Form the differential equation of the family of curves, y=a sin (bx+c), Where a…
  4. Form the differential equation of the family of curves x=A cos nt+ Bsin nt,…
  5. Form the differential equation of the family of curves y=aebx, where a and b…
  6. Form the differential equation of the family of curves y2=m(a2-x2), where a and…
  7. Form the differential equation of the family of curves given by (x-a)2+2y2=a2,…
  8. Form the differential equation of the family of curves given by x2+y2-2ay=a2,…
  9. Form the differential equation of the family of all circles touching the y-axis…
  10. From the differential equation of the family of circles having centers on…
  11. Form the differential equation of the family of circles in the second quadrant…
  12. Form the differential equation of the family of circles having centers on the…
  13. Form the differential equation of the family of circles passing through the…
  14. Form the differential equation of the family of parabolas having a vertex at…
  15. Form the differential equation of the family of an ellipse having foci on the…
  16. Form the differential equation of the family of hyperbolas having foci on the…

Exercise 18a
Question 1.

Write order and degree (if defined)of each of the following differential equations:




Answer:

The order of a differential equation is the order of the highest derivative involved in the equation. So the order comes out to be 4 as we have and the degree is the highest power to which a derivative is raised. But when we open the Cos x series, we get This leads to an undefined power on the highest derivative. Therefore the deg9ee of this function becomes undefined.

So the answer is 4, not defined.



Question 2.

Write order and degree (if defined)of each of the following differential equations:




Answer:

The order of a differential equation is the order of the highest derivative involved in the equation. So the order comes out to be 2 as we have and the degree is the highest power to which a derivative is raised. So the power at this order is 1.

So the answer is 2, 1.



Question 3.

Write order and degree (if defined)of each of the following differential equations:




Answer:

The order of a differential equation is the order of the highest derivative involved in the equation. So the order comes out to be 2 as we have and the degree is the highest power to which a derivative is raised. So the power at this order is 2.

So the answer is 2, 2.



Question 4.

Write order and degree (if defined)of each of the following differential equations:




Answer:

The order of a differential equation is the order of the highest derivative involved in the equation. So the order comes out to be 2 as we have and the degree is the highest power to which a derivative is raised. So the power at this order is 2.

So the answer is 2, 2.



Question 5.

Write order and degree (if defined)of each of the following differential equations:




Answer:

The order of a differential equation is the order of the highest derivative involved in the equation. So the order comes out to be 3 as we have and the degree is the highest power to which a derivative is raised. So the power at this order is 2.

So the answer is 3, 2.



Question 6.

Write order and degree (if defined)of each of the following differential equations:




Answer:

The order of a differential equation is the order of the highest derivative involved in the equation. So the order comes out to be 2 as we have and the degree is the highest power to which a derivative is raised. So the power at this order is 1.

So the answer is 2, 1.



Question 7.

Write order and degree (if defined)of each of the following differential equations:




Answer:

The order of a differential equation is the order of the highest derivative involved in the equation. So the order comes out to be 1 as we have and the degree is the highest power to which a derivative is raised. So the power at this order is 1. Also, the equation has to be a polynomial, but here the exponential function does not take any derivative with this. Hence it is a polynomial.

So the answer is 1, 1.



Question 8.

Write order and degree (if defined)of each of the following differential equations:




Answer:

The order of a differential equation is the order of the highest derivative involved in the equation. So the order comes out to be 2 as we have and the degree is the highest power to which a derivative is raised. But here when we open the series of as . Also, the equation has to be polynomial. Therefore the degree is not defined. Also, the equation has to be a polynomial, but opening the exponential function will give undefined power to the highest derivative, so the degree of this function is not defined.

So the answer is 2, not defined .



Question 9.

Write order and degree (if defined)of each of the following differential equations:




Answer:

The order of a differential equation is the order of the highest derivative involved in the equation. So the order comes out to be 1 as we have and the degree is the highest power to which a derivative is raised. But when we open Sin x as . Also, the equation has to be polynomial, and opening thus, Sin function will lead to an undefined power of the highest derivative. Therefore the degree is not defined.

So the answer is 1, not defined.



Question 10.

Write order and degree (if defined)of each of the following differential equations:




Answer:

The order of a differential equation is the order of the highest derivative involved in the equation. So the order comes out to be 2 as we have and the degree is the highest power to which a derivative is raised. So the power at this order is 1. Because the logarithm function is not at any derivative, so it doesn’t destroy the polynomial.Hence degree is 1

So the answer is 2, 1.



Question 11.

Write order and degree (if defined)of each of the following differential equations:




Answer:

The order of a differential equation is the order of the highest derivative involved in the equation. So the order comes out to be 1 as we have and the degree is the highest power to which a derivative is raised. So the power at this order is 3. Because the Sine function is not at any derivative, so it doesn’t destroy the polynomial.Hence the degree is 3.


So the answer is 1, 3.



Question 12.

Write order and degree (if defined)of each of the following differential equations:




Answer:

The order of a differential equation is the order of the highest derivative involved in the equation. So the order comes out to be 3 as we have and the degree is the highest power to which a derivative is raised. So the power at this order is 1.

So the answer is 3, 1.



Question 13.

Write order and degree (if defined)of each of the following differential equations:




Answer:

The order of a differential equation is the order of the highest derivative involved in the equation. So the order comes out to be 1 as we have

and the degree is the highest power to which a derivative is raised. So the power at this order is 2.


So the answer is 1, 2.



Question 14.

Write order and degree (if defined)of each of the following differential equations:




Answer:

The order of a differential equation is the order of the highest derivative involved in the equation. So the order comes out to be 2/3 as we have


and the degree is the highest power to which a derivative is raised. So the power at this order is 2.


So the answer is 2/3, 2.



Question 15.

Write order and degree (if defined)of each of the following differential equations:




Answer:

The order of a differential equation is the order of the highest derivative involved in the equation. So, the order comes out to be 1 as we have



and the degree is the highest power to which a derivative is raised. So the power at this order is 1.


So the answer is 1, 1.



Question 16.

Write order and degree (if defined)of each of the following differential equations:




Answer:

The order of a differential equation is the order of the highest derivative involved in the equation. So, the order comes out to be 3 as we have


and the degree is the highest power to which a derivative is raised. So the power at this order is 2.


So the answer is 3, 2.



Question 17.

Write order and degree (if defined)of each of the following differential equations:

(3x + 5y)dy - 4x2 dx = 0


Answer:

The order of a differential equation is the order of the highest derivative involved in the equation. So, the order comes out to be 1 as we have (3x + 5y)dy - 4x2 dx = 0


and the degree is the highest power to which a derivative is raised. So the power at this order is 1.


So the answer is 1, 1.



Question 18.

Write order and degree (if defined)of each of the following differential equations:




Answer:

Given:


Solving, we get,



Now,


The order of a differential equation is the order of the highest derivative involved in the equation. So, the order comes out to be 2 as we have,


and the degree is the highest power to which a derivative is raised. So the power at this order is 1.


So the answer is 2, 1.




Exercise 18b
Question 1.

Verify that x2 = 2y2log y is a solution of the differential equation (x2 + y2) - xy = 0.


Answer:

Given


On differentiating both sides with respect to x, we get





Multiply both sides with y



We know, . So replace with in the above equation.




Conclusion: Therefore is the solution of



Question 2.

Verify that x2 = 2y2log y is a solution of the differential equation (x2 + y2) - xy = 0.


Answer:

Given


On differentiating both sides with respect to x, we get





Multiply both sides with y



We know, . So replace with in the above equation.




Conclusion: Therefore is the solution of



Question 3.

Verify that y = ex cos bx is a solution of the differential equation


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get



Now let’s see what is the value of




This is not a solution


Conclusion: Therefore, y = ex cos bx is not the solution of



Question 4.

Verify that y = ex cos bx is a solution of the differential equation


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get



Now let’s see what is the value of




This is not a solution


Conclusion: Therefore, y = ex cos bx is not the solution of



Question 5.

Verify that y = is a solution of the differential equation (1 - x2)


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get



We want to find



= 0


Therefore, is the solution of


Conclusion: Therefore, is the solution of




Question 6.

Verify that y = is a solution of the differential equation (1 - x2)


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get



We want to find



= 0


Therefore, is the solution of


Conclusion: Therefore, is the solution of




Question 7.

Verify that y = (a + bx) e2x is the general solution of the differential equation


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get



Now let’s see what is the value of



= 0


Conclusion: Therefore, is the solution of



Question 8.

Verify that y = (a + bx) e2x is the general solution of the differential equation


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get



Now let’s see what is the value of



= 0


Conclusion: Therefore, is the solution of



Question 9.

Verify that y = ex(A cos x + B sin x) is the general solution of the differential equation


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get




Now let’s see what is the value of



= 0


Conclusion: Therefore, is the solution of



Question 10.

Verify that y = ex(A cos x + B sin x) is the general solution of the differential equation


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get




Now let’s see what is the value of



= 0


Conclusion: Therefore, is the solution of



Question 11.

Verify that y = A cos 2x - B sin 2x is the general solution of the differential equation = 0.


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get



Now let’s see what is the value of



= 0


Conclusion: Therefore, is the solution of



Question 12.

Verify that y = A cos 2x - B sin 2x is the general solution of the differential equation = 0.


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get



Now let’s see what is the value of



= 0


Conclusion: Therefore, is the solution of



Question 13.

Verify that y = ae2x + be - x is the general solution of the differential equation


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get



Now let’s see what is the value of



= 0


Conclusion : Therefore, is the solution of



Question 14.

Verify that y = ae2x + be - x is the general solution of the differential equation


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get



Now let’s see what is the value of



= 0


Conclusion : Therefore, is the solution of



Question 15.

Show that y = ex(A cos x + B sin x) is the solution of the differential equation


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get



Now let’s see what is the value of



= 0


Conclusion: Therefore, is the solution of




Question 16.

Show that y = ex(A cos x + B sin x) is the solution of the differential equation


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get



Now let’s see what is the value of



= 0


Conclusion: Therefore, is the solution of




Question 17.

Verify that y2 = 4a(x + a) is a solution of the differential equation


Answer:

Given,


On differentiating with x, we get



Now let’s see what is the value of






= 0


Conclusion: Therefore, is the solution of



Question 18.

Verify that y2 = 4a(x + a) is a solution of the differential equation


Answer:

Given,


On differentiating with x, we get



Now let’s see what is the value of






= 0


Conclusion: Therefore, is the solution of



Question 19.

Verify that y = is a solution of the differential equation (1 + x2) + (2x - 1) = 0


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get




Now let’s see what is the value of




Conclusion: Therefore, is not the solution of




Question 20.

Verify that y = is a solution of the differential equation (1 + x2) + (2x - 1) = 0


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get




Now let’s see what is the value of




Conclusion: Therefore, is not the solution of




Question 21.

Verify that y = is a solution of the differential equation


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get



Now let’s see what is the value of




= 0


Conclusion: Therefore, is the solution of



Question 22.

Verify that y = is a solution of the differential equation


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get



Now let’s see what is the value of




= 0


Conclusion: Therefore, is the solution of



Question 23.

Verify that y = is a solution of the differential equation


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get



Now let’s see what is the value of



= 0


Conclusion: Therefore, is the solution of



Question 24.

Verify that y = is a solution of the differential equation


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get



Now let’s see what is the value of



= 0


Conclusion: Therefore, is the solution of



Question 25.

Verify that y = e- x + Ax + B is a solution of the differential equation


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get



Now let’s see what is the value of



= 1


Conclusion: Therefore, is the solution of



Question 26.

Verify that y = e- x + Ax + B is a solution of the differential equation


Answer:

Given


On differentiating with x, we get



On differentiating again with x, we get



Now let’s see what is the value of



= 1


Conclusion: Therefore, is the solution of



Question 27.

Verify that Ax2 + By2 = 1 is a solution of the differential equation


Answer:

Given


On differentiating with x, we get




On differentiating again with x, we get




Now let’s see what is the value of




= 0


Conclusion: Therefore, is the solution of




Question 28.

Verify that Ax2 + By2 = 1 is a solution of the differential equation


Answer:

Given


On differentiating with x, we get




On differentiating again with x, we get




Now let’s see what is the value of




= 0


Conclusion: Therefore, is the solution of




Question 29.

Verify that y = is a solution of the differential equation (1 + x2) + (1 + y2) = 0.


Answer:

Given


On differentiating with x, we get



Now let’s see what is the value of




= 0


Conclusion: Therefore, is the solution of



Question 30.

Verify that y = is a solution of the differential equation (1 + x2) + (1 + y2) = 0.


Answer:

Given


On differentiating with x, we get



Now let’s see what is the value of




= 0


Conclusion: Therefore, is the solution of



Question 31.

Verify that y = log (x + satisfies the differential equation.


Answer:

Given


On differentiating with x, we get




On differentiating again with x, we get



Now let’s see what is the value of



Conclusion: Therefore, is not the solution of




Question 32.

Verify that y = log (x + satisfies the differential equation.


Answer:

Given


On differentiating with x, we get




On differentiating again with x, we get



Now let’s see what is the value of



Conclusion: Therefore, is not the solution of




Question 33.

Verify that y = e - 3x is a solution of the differential equation


Answer:

Given,


On differentiating with x, we get



On differentiating again with x, we get



Now let’s see what is the value of



= 0


Conclusion: Therefore, is the solution of



Question 34.

Verify that y = e - 3x is a solution of the differential equation


Answer:

Given,


On differentiating with x, we get



On differentiating again with x, we get



Now let’s see what is the value of



= 0


Conclusion: Therefore, is the solution of




Exercise 18c
Question 1.

Form the differential equation of the family of straight lines y=mx+c, where m and c are arbitrary constants.


Answer:

The equation of a straight line is represented as,

Y = mx + c


Differentiating the above equation with respect to x,



Differentiating the above equation with respect to x,



This is the differential equation of the family of straight lines y=mx+c, where m and c are arbitrary constants



Question 2.

Form the differential equation of the family of concentric circles x2+y2=a2, where a>0 and a is a parameter.


Answer:

Now, in the general equation of of the family of concentric circles x2+y2=a2, where a>0, ‘a’ represents the radius of the circle and is an arbitrary constant.

The given equation represents a family of concentric circles centered at the origin.


x2+y2=a2


Differentiating the above equation with respect to x on both sides, we have,


(As a>0, derivative of a with respect to x is 0.)




Question 3.

Form the differential equation of the family of curves, y=a sin (bx+c), Where a and c are parameters.


Answer:

Equation of the family of curves, y=a sin (bx+c), Where a and c are parameters.

Differentiating the above equation with respect to x on both sides, we have,


(1)



(Substituting equation 1 in this equation)




This is the required differential equation.



Question 4.

Form the differential equation of the family of curves x=A cos nt+ Bsin nt, where A and B are arbitrary constants.


Answer:

Equation of the family of curves, x=A cos nt+ Bsin nt, where A and B are arbitrary constants.

Differentiating the above equation with respect to t on both sides, we have,


(1)




(Substituting equation 1 in this equation)




This is the required differential equation.



Question 5.

Form the differential equation of the family of curves y=aebx, where a and b are arbitrary constants.


Answer:

Equation of the family of curves, y=aebx, where a and b are arbitrary constants.

Differentiating the above equation with respect to x on both sides, we have,


(1)


(2)



(Multiplying both sides of the equation by y)


(Substituting equation 2 in this equation)



This is the required differential equation.



Question 6.

Form the differential equation of the family of curves y2=m(a2-x2), where a and m are parameters.


Answer:

Equation of the family of curves, y2=m(a2-x2), where a and m are parameters.

Differentiating the above equation with respect to x on both sides, we have,




(1)


Differentiating the above equation with respect to x on both sides,


(2)


From equations (1) and (2),



This is the required differential equation.



Question 7.

Form the differential equation of the family of curves given by (x-a)2+2y2=a2, where a is an arbitrary constant.


Answer:

Equation of the family of curves, (x-a)2+2y2=a2, where a is an arbitrary constant.


(1)


Differentiating the above equation with respect to x on both sides, we have,






(Substituting 2ax from equation 1)




This is the required differential equation.



Question 8.

Form the differential equation of the family of curves given by x2+y2-2ay=a2, where a is an arbitrary constant.


Answer:

Equation of the family of curves, x2+y2-2ay=a2, where a is an arbitrary constant.


(1)


Differentiating the above equation with respect to x on both sides, we have,






(Substituting 2ax from equation 1)




This is the required differential equation.



Question 9.

Form the differential equation of the family of all circles touching the y-axis at the origin.


Answer:

Equation of the family of all circles touching the y-axis at the origin can be represented by

(x-a)2+y2=a2, where a is an arbitrary constants.


(1)


Differentiating the above equation with respect to x on both sides, we have,





Substituting the value of a in equation (1)




Rearranging the above equation



This is the required differential equation.



Question 10.

From the differential equation of the family of circles having centers on y-axis and radius 2 units.


Answer:

Equation of the family of circles having centers on y-axis and radius 2 units can be represented by

(x)2+(y – a)2= 4, where a is an arbitrary constant.


(1)


Differentiating the above equation with respect to x on both sides, we have,





Substituting the value of a in equation (1)





Rearranging the above equation



This is the required differential equation.



Question 11.

Form the differential equation of the family of circles in the second quadrant and touching the coordinate axes


Answer:

Equation of the family of circles in the second quadrant and touching the coordinate axes

can be represented by


(x – (-a))2+(y – a)2= a2, where a is an arbitrary constants.


(1)


Differentiating the above equation with respect to x on both sides, we have,





Substituting the value of a in equation (1)







Rearranging the above equation



This is the required differential equation.



Question 12.

Form the differential equation of the family of circles having centers on the x-axis and radius unity.


Answer:

Equation of the family of circles having centers on the x-axis and radius unity can be represented by

(x - a)2+(y)2= 1, where a is an arbitrary constants.


(1)


Differentiating the above equation with respect to x on both sides, we have,





Substituting the value of a in equation (1)




This is the required differential equation.



Question 13.

Form the differential equation of the family of circles passing through the fixed point (a,0) and (-a,0), where a is the parameter.


Answer:

Now, it is not necessary that the centre of the circle will lie on origin in this case. Hence let us assume the coordinates of the centre of the circle be (0, h). Here, h is an arbitrary constant.

Also, the radius as calculated by the Pythagoras theorem will be a2 + h2.


Hence, the equation of the family of circles passing through the fixed point (a,0) and (-a,0), where a is the parameter can be represented by


(x)2+(y – h)2= a2 + h2, where a is an arbitrary constants.


(1)


Differentiating the above equation with respect to x on both sides, we have,





Substituting the value of a in equation (1)








This is the required differential equation.



Question 14.

Form the differential equation of the family of parabolas having a vertex at the origin and axis along positive y-axis.


Answer:

Equation of the family of parabolas having a vertex at the origin and axis along positive y-axis can be represented by

(x)2 = 4ay, where a is an arbitrary constants.


(1)


Differentiating the above equation with respect to x on both sides, we have,





Substituting the value of a in equation (1)




This is the required differential equation.



Question 15.

Form the differential equation of the family of an ellipse having foci on the y-axis and centers at the origin.


Answer:

Equation of the family of an ellipse having foci on the y-axis and centers at the origin can be represented by

(1)


Differentiating the above equation with respect to x on both sides, we have,






Again differentiating the above equation with respect to x on both sides, we have,




Rearranging the above equation



This is the required differential equation.



Question 16.

Form the differential equation of the family of hyperbolas having foci on the x-axis and centers at the origin.


Answer:

Equation of the family of an ellipse having foci on the y-axis and centers at the origin can be represented by

(1)


Differentiating the above equation with respect to x on both sides, we have,






Again differentiating the above equation with respect to x on both sides, we have,




Rearranging the above equation



This is the required differential equation.