\documentclass{minimal}
\usepackage{amsmath}
\begin{document}

\[
  f(x) = 1
\]

{Stuff here
  asdasd}

\begin{equation}
  \left(
    f(x) = 3
    \right)
  \left.
    f(x) = 3
    \right.
\end{equation}
\end{document}