NTA Abhyas JEE Main2020MathematicsDifferential EquationsPractice
The solution of the differential equation d y d x + x y ln y = x 3 y is equal to (where, C is the constant of integration)
Options
- Aln y = x 2 + C e - x 2
- Bln y = x 2 - 2 + C e - x 2
- Cln y = x 2 - 2 + C e - x 2 2
- Dln y = x 2 + C e - x 2 2
Correct answer
C. ln y = x 2 - 2 + C e - x 2 2
Step-by-step solution
1 y d y d x + x ln y = x 3 Let ln y = t 1 y d y d x = d t d x d t d x + t x = x 3 I.F. = e ∫ x d x = e x 2 2 t e x 2 2 = ∫ e x 2 2 x 3 d x ln y e x 2 2 = ∫ e x 2 2 ⋅ x x 2 d x ln y e x 2 2 = e x 2 2 ⋅ x 2 - ∫ 2 x e x 2 2 d x ln e x 2 2 = e x 2 2 x 2 - 2 e x 2 2 + C ln y ⋅ e x 2 2 = e x 2 2 x 2 - 2 + C ln y = x 2 - 2 + C e - x 2 2