documentclass[DIV=16]{scrartcl}
usepackage{tikz}
pagestyle{empty}
begin{document}
hrule
begin{center}
begin{tikzpicture}[scale=.3]
    draw[domain=-1:5] plot (x,{0.5*x*x*(x-3)});
end{tikzpicture}
end{center}
hrule
begin{center}
begin{tikzpicture}[scale=.3]
    draw (-1,-2) .. controls (1,7) and (3,-20) .. (5,25);
end{tikzpicture}
end{center}
hrule
end{document}