Function satisfing : $h(x)=f(2x-1)$ with $f'(-1)=0 $ and $f'(2)=-2$ then what is $h'(x) $?

Question

I find in some book this function defined as follow $h(x)=f(2x-1)$ .

with $f'(2)=-2 $ and $f'(-1)=0$ , we would like to know $h'(3/2)$ ?

In the book take $h'(x)=f'(2x-1)=(f'(2))x+f'(-1)=-2x $

but i know $f(2x-1)$ is a composition of two function ,why they didn't take

$h'(x)=2f'(2x-1)$ ?

Thank you for any help !!!