![PSTricks 绘图错误](https://linux22.com/image/344313/PSTricks%20%E7%BB%98%E5%9B%BE%E9%94%99%E8%AF%AF.png)
我想绘制一条抛物线并使用以下代码:
\usepackage{pst-plot}
\usepackage{pst-math}
%...
\begin{pspicture}(-2,-3.5)(6,3)
\psgrid[griddots=10,gridlabels=0pt,subgriddiv=0,gridcolor=black!20]
\psaxes(0,0)(-2,-3.5)(6,3)
\psset{algebraic,linewidth=1.5pt}
\psplot[linecolor=red]{-1}{5}{-0.5(x-2)^2+2}
\end{pspicture}