Answer:
is the answer
given
and
.
Explanation:


Inputting the given function for h(x) into the above:

Now we are plugging in g(x) for x in the expression for f which is
which gives us
:

We want to solve this for g(x).
If you don't like the looks of g(x) (if you think it is too daunting to look at), replace it with u and solve for u.

Divide both sides by 4:

Square both sides:

Subtract 1 on both sides:

Simplify left hand side:


Remember u was g(x) so you just found g(x) so congratulations.
.
Let's check it:


I replace g(x) with x+6 since g(x)=x+6.
I replace x in f with (x+6).



The check is done. We have that
.