`f: RvecR ,f(x)` is differentiable such that `f(f(x))=k(x^5+x),k!=0)dot` Then `f(x)` is always increasing (b) decreasing either increasing or decreasing non-monotonic

Options

A. increasing
B. decreasing on `[-1//2,oo]`
C. either increasing or decreasing
D. non monotonic

Answer

3

Explanation

`f(f(x))=k(x^(5)+x)or f'(f(x))f'(x)=k(5x^(4)+1)`
Thus f(x) is always increasing or decreasing as `k(5x^(4)+1)` is eitehr always negative or positive .