\documentclass{ppex}
\nonstopmode
\usepackage {mfpic}
\pagestyle{empty}
\setlength\textwidth{207.0pt}
\begin{document}
\ResetPreambleCommands
\ReadyForTheFray
\usepackage {mfpic}
\begin{mfpic}[15]{-3}{3}{-3}{3}
\axes
\function{-2,2,0.1}{((x**3)-x)/2}
\end{mfpic}
\end{document}