JEE Main20199 Apr 2019Evening ShiftMathematicsDefinite IntegrationActual
If f : R → R is a differentiable function and f 2 = 6 , then l i m x → 2 ∫ 6 f x 2 t d t x - 2 is:
Options
- A0
- B2 f ' 2
- C24 f ' 2
- D12 f ' 2
Correct answer
D. 12 f ' 2
Step-by-step solution
The given limit can be written as l = lim x → 2 ∫ 6 f x 2 t d t x - 2     Applying L' Hospital’s rule i.e. if l = lim x → a g x h x and lim x → a g x → 0   &   lim x → a h x → 0 , then l = lim x → a g ' x h ' x l = l i m x → 2 d d x ∫ 6 f x 2 t d t 1 Now, applying Newton's Leibnitz rule i.e. d d x ∫ a b g x d x = g b · b ' - g a · a ' , we get ⇒ l = lim x → 2 2 f x · f ' x - 0 &