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%%  Die DANTE-Edition
%%  Ein Beispiel der LaTeX Referenz
%%  3. Auflage
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%%  Copyright (C) 2013 Herbert Voss
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%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
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%%  See http://www.latex-project.org/lppl.txt for details.
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\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{193.16928pt}
%StartShownPreambleCommands
\usepackage{amsmath,empheq,xcolor}
%StopShownPreambleCommands
\begin{document}
\begin{empheq}[box=\fcolorbox{blue}{yellow!40}]{align}
y      &= d                  & z &= 1        \nonumber\\
y      &= cx+d               & z &= x+1               \\
y_{12} &= bx^{2}+cx+d        & z &= x^{2}+x+1\nonumber
\end{empheq}
\end{document}