Let $\displaystyle f(x) = x + 4$ and $\displaystyle h(x) = 4x - 1$. Find a function $\displaystyle g$ such that $\displaystyle g \circ f = h$.

$\displaystyle g(f(x)) = h$

$\displaystyle g(f) = h$

$\displaystyle g(x + 4) = 4x - 1$

$\displaystyle g = \frac {4x - 1}{x + 4}$

And textbook answer is $\displaystyle g(x) = 4x - 17$

I don't know how to get the textbook answer.......?