JEE Main202225 Jul 2022Morning ShiftMathematicsDifferential EquationsActual
The general solution of the differential equation x - y 2 d x + y 5 x + y 2 d y = 0 is
Options
- Ay 2 + x 4 = C y 2 + 2 x 3
- By 2 + 2 x 4 = C y 2 + x 3
- Cy 2 + x 3 = C 2 y 2 + x 4
- Dy 2 + 2 x 3 = C 2 y 2 + x 4
Correct answer
A. y 2 + x 4 = C y 2 + 2 x 3
Step-by-step solution
Given, x - y 2 d x + y 5 x + y 2 d y = 0 After rearranging we get, d y d x = y 2 - x y 5 x + y 2 Now, let y 2 = v ⇒ 2 y d y d x = d v d x 1 2 y d v d x = v - x y 5 x + v d v d x = 2 v - x 5 x + v Now let v = k x ⇒ k + x d k d x = 2 k x - x 5 x + k x ⇒ x d k d x = - k 2 + 3 k + 2 k + 5 ⇒ ∫ 5 + k k + 1 k + 2 d k = ∫ - d x x ⇒ ∫ 4 k + 1 - 3 k + 2 d k = - ∫ d x x ⇒ 4 ln k + 1 - 3 ln k + 2 = - ln x + ln c ⇒ k + 1 4 k + 2 3 = c x ⇒ v x + 1 4 v x + 2