k(x) = f(x^4). Which of the following is k''(x)?
a. 2xf''(x^2)
b. 4x^2f''(x^2)
c. (4x^2+2x)(f''(x^2))
d. 4x^2f''(x^2)+2f'(x^2)
e. 4x^2f''(x^2)+2xf'(x^2)
Since all the answers use f'(x^2), I assume that you meant
k(x) = f(x^2)
k'(x) = f'(x^2)*2x
k"(x) = f"(x^2)*2x*2x + 2f'(x^2)
So, (d)
check an example, such as
k(x) = sin(x^2)