\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}
