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%%  Die DANTE-Edition
%%  Ein Beispiel der LaTeX Referenz
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%%  Copyright (C) 2013 Herbert Voss
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%%  It may be distributed and/or modified under the conditions
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\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{352.81416pt}
%StartShownPreambleCommands
\usepackage{amsmath}
%StopShownPreambleCommands
\begin{document}
\begin{alignat}{2}
y      &= d & z & =1                           \\
y      &= cx+d & z & =x+1                      \\
y_{12} &= bx^{2}+cx+d & z &=x^{2}+x+1\nonumber
\end{alignat}
\end{document}