Functions use the notation $f(x)$. To evaluate, substitute the value: if $f(x)=2x+1$ then $f(3)=2(3)+1=7$.
A composite function $fg(x)$ means "do $g$ first, then $f$". The inverse $f^{-1}(x)$ reverses the function.
Remember
- $f(3)$ means substitute $x=3$.
- $f^{-1}$ = inverse; $fg$ = do $g$ then $f$.