You may want to review composing functions and other operations on them first.

You can also compute *f*(*g*(*x*)). You just plug
the expression for *g* into *f*. For example,
if *f*(*x*) = −*x* and *g*(*x*) =
−2*x* + 1, then *f*(*g*(*x*)) =
−(−2*x* + 1), which of course simplifies to
2*x* − 1.