Given :
$\displaystyle f(h(x)) = \sqrt{(x^2+9)}$
and
$\displaystyle h(x) = x^2 + 9$
find : $\displaystyle h(f(x))$
Thanks in advance
I'm a bit confused as to what the difficulty is. If you are told that
$\displaystyle f(h(x))= \sqrt{(x^2+ 9)}$ and that $\displaystyle h(x)= x^2+ 9$ then it should be obvious that $\displaystyle f(x)= \sqrt{x}$. From that, $\displaystyle h(f(x))= (\sqrt{x})^2+ 9= x+ 9$.