Answer
$f[g(x)]=g[f(x)]=x$. this means that $f(x)$ and $g(x)$ are inverses of each other.
Both $f(x)$ and $g(x)$ are continuous on the set of real numbers, so there are no restrictions to their domains and no values to be excluded.
Work Step by Step
We wish to plug $f(x)$ into $g(x)$ to obtain:
$$\displaystyle g[f(x)]=g (x) =x$$
We wish to plug $g(x)$ into $f(x)$ to obtain:
$$f[(g(x)]=f (x) =x$$
We see that $f[g(x)]=g[f(x)]=x$. This means that $f(x)$ and $g(x)$ are inverses of each other.
Both $f(x)$ and $g(x)$ are continuous on the set of real numbers, so there are no restrictions to their domains and no values to be excluded.
