\documentclass[a4paper]{article}

\usepackage{pst-eps}

\pagestyle{empty}

\begin{document}
\thispagestyle{empty}

\TeXtoEPS
\large
$ v = \left\{ \begin{array}{ll}
                 ax^2 + bx +c & \mbox{if root=false} \\
                 \sqrt{ax^2+bx+c} & \mbox{otherwise}
              \end{array} \right. $
\endTeXtoEPS


\end{document}