%% Autor: X. Rendtel 
%% Letzte Aenderung: 23.11.2008
 
\documentclass[10pt, a4paper]{article}
\usepackage[utf8x]{inputenc}
\usepackage{euler,calc,pstricks,rotating,graphicx,multido}
\usepackage{pst-pdf,pst-node,xcolor,pst-circ,pst-func,pst-math,pst-eucl,pstricks-add}
\usepackage[greek,german]{babel}
\usepackage[LGR,T1]{fontenc}
\usepackage{mathpazo,avant,courier}
 
\makeatletter\newcommand{\psxpoint}[3][black]{%
  \psline[linewidth=.5pt]{-}(#2,\pst@xticksizeB)(#2,\pst@xticksizeA)
  \rput[t](! #2 \pst@number\pslabelsep \pst@number\pst@xticksizeB add
    \pst@number\psyunit div neg ){\color{#1}#3}}
\makeatother

\makeatletter\newcommand{\psypoint}[3][black]{%
  \psline[linewidth=.5pt]{-}(\pst@yticksizeB,#2)(\pst@yticksizeA,#2)
  \rput[r](! \pst@number\pslabelsep \pst@number\pst@yticksizeA sub
    \pst@number\psxunit div neg #2){\color{#1}#3}}
\makeatother
 
\newcommand{\EUR}{\textgreek{\euro}}
\pagestyle{empty}
\begin{document}
  
\psset{
 dotstyle = *, plotpoints=10000, 
 dotsize = 3pt,
 linewidth = 3pt,
 linecolor = black,
 arrowsize = 3pt 2,
 arrowinset = 0.25,
 xunit = 1cm,
 yunit = 1cm,
 algebraic = true} 
 
\begin{pspicture}(-4.3,-5.2)(5.2,5.2)
 
% Ein Koordinatensystem wird gezeichnet 
\psaxes [
 comma,
 showorigin = false,
 Dx = 1,
 Dy = 1,
 dx = 0 pt,
 dy = 0 pt,
 Ox = 0,
 Oy = 0, 
linewidth = 0.8pt,
 linestyle = solid]{->}% 
(0,0) 
(-4,-4) 
(4,4) 
\uput{0}[-90]{0}(4.2,-0.2){$x$} 
\uput{0}[0]{0}(0.2,4){$y$} 
 
% Text 
\uput{0}[0]{0}(2,4.2){$y=x^2$} 
% Text 
\uput{0}[0]{0}(2,-4.2){$y=-x^2$} 
% Text 
\uput{0}[0]{0}(-1.5,4.2){\color{blue}{$y=2\cdot x^2$}} 
% Text 
\uput{0}[0]{0}(-1.5,-4.2){\color{blue}{$y=-2\cdot x^2$}} 
% Text 
\uput{0}[0]{0}(-3.3,4.2){\color{red}{$y=\frac{1}{2}\cdot x^2$}} 
% Text 
\uput{0}[0]{0}(-3.3,-4.2){\color{red}{$y=-\frac{1}{2}\cdot x^2$}} 
% Ein Graph wird gezeichnet 
\psplot[
 linewidth = 1pt,
 linestyle = solid]% 
{-1.9980}{1.9947}{x^2} 
 
% Ein Graph wird gezeichnet 
\psplot[
 linewidth = 1pt,
 linestyle = solid]% 
{-1.9980}{1.9947}{-x^2} 
 
% Ein Graph wird gezeichnet 
\psplot[
 linecolor = blue,
 linewidth = 1pt,
 linestyle = solid]% 
{-1.4134}{1.4098}{2*x^2} 
 
% Ein Graph wird gezeichnet 
\psplot[
 linecolor = blue,
 linewidth = 1pt,
 linestyle = solid]% 
{-1.4134}{1.4098}{-2*x^2} 
 
% Ein Graph wird gezeichnet 
\psplot[
 linecolor = red,
 linewidth = 1pt,
 linestyle = solid]% 
{-2.8228}{2.8253}{0.5*x^2} 
 
% Ein Graph wird gezeichnet 
\psplot[
 linecolor = red,
 linewidth = 1pt,
 linestyle = solid]% 
{-2.8228}{2.8253}{-0.5*x^2} 
 
\end{pspicture} 
\end{document}