NTA Abhyas JEE Main2020MathematicsDifferentiationPractice
Let f x is a differentiable function on x ∈ R , such that f x + y = f x f y for all x , y ∈ R where f 0 ≠ 0 . If f 5 = 10 ,   f ' 0 = 6 , then the value of f ′ 5 is equal to
Correct answer
60
Step-by-step solution
f ′ 5 = lim h → 0 f 5 + h − f 5 h = l i m h → 0 f 5 + h - f 5 + 0 h = l i m h → 0 f 5 . f h - f 5 . f 0 h [ ∵   f x + y = f x . f y   f o r   a l l  x , y ] = l i m h → 0 f h - f 0 h . f 5 = f ′ 0 . f 5 = 6 × 10 = 60