You may want to review operations on functions first.

Another thing you can do to two functions is to *compose*
them. That means you apply one and then the other. For example,
if *f*(*x*) = −2*x* + 1
and *g*(*x*) = *x*^{2} − 1, you could
be asked for *f*(*g*(−1)). First, you
find *g*(−1), which is 0. Then, you find *f*(0),
which is 1, so that's the answer.

Remember to always apply the inner function first!