NTA Abhyas JEE Main2020MathematicsDefinite IntegrationPractice
For x ∈ R , x ≠ 0 , if y x is a differentiable function such that x ∫ 1 x y t d t = x + 1 ∫ 1 x t y t d t , then y x equals (where C is a constant)
Options
- AC x 3 e 1 x
- BC x 2 e - 1 x
- CC x e - 1 x
- DC x 3 e - 1 x
Correct answer
D. C x 3 e - 1 x
Step-by-step solution
x ∫ 1 x y t d t = x ∫ 1 x t y t d t + ∫ 1 x t y t d t Differentiate w.r.t. x ∫ 1 x y ( t ) d t + x y ( x ) = ∫ 1 x t y ( t ) d t + x [ x y ( x ) ] + x y ( x ) ∫ 1 x y ( t ) d t = ∫ 1 x t y ( t ) d t + x 2 y ( x ) Differentiate again w.r.t. x y ( x ) = x y ( x ) + 2 x y ( x ) + x 2 y ' ( x ) 1 - 3 x y x = x 2 y ' x y ' x y x = 1 - 3 x x 2 1 y d y d x = 1 - 3 x x 2 Integrating on both sides ⇒ l o g y = - 1 x - 3 l o g x + c ⇒ l o g ( y x 3 ) = - 1 x + c ⇒ y x 3 = e - 1 x + c ⇒ y = e - 1 x + c x 3 ⇒ y = C x 3 e - 1 x