\textbf{108-} The function $f(x) = x^2 + 2x + 1$ with domain $(-\infty, +\infty)$ is assumed to be invertible. The graphs of $f$ and $f^{-1}$ intersect at how many points?
\begin{itemize}
\item[(1)] $1$
\item[(2)] $2$
\item[(3)] $3$
\item[(4)] No intersection
\end{itemize}