NDA2015MathematicsDifferential EquationsActual
The differential equation of the family of circles passing through the origin and having centres on the x -axis is
Options
- A2 x y d y d x =x^2-y^2
- B2 x y d y d x =y^2-x^2
- C2 x y d y d x =x^2+y^2
- D2 x y d y d x +x^2+y^2=0
Correct answer
B. 2 x y d y d x =y^2-x^2
Step-by-step solution
Eq. of family of circles passing through the origin & having centres on the x -axis is: aligned & x^2+y^2+2 g x=0 & 2 x+2 y d y d x +2 g=0 & g=- [x+y d y d x ] aligned [on differentiating] Putting the value of (g) in eq. (1) we get; 2 x y d y d x =y^2-x^2