Let f(x)=x5+2ex / 4 for all x R. Consider a function g(x) such that (g f)(x)=x for all x R. Then the value of 8 g (2) is :
- 4
- 2
- 16
- 8
Answer
(3) 16
Solution
g(f(x))=x g'(f(x)) f'(x)=1 (chain rule)
f(0)=0+2e0=2 and f'(x)=5x4+ 12ex/4 f'(0)= 12
Put x=0: g'(2) 12=1 g'(2)=2
8g'(2)=16
Answer: (3)