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%%  Ein Beispiel der DANTE-Edition
%%  Mathematiksatz mit LaTeX
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%%  Beispiel 10-01-2 auf Seite 212.
%%  Copyright (C) 2018 Herbert Voss
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\begin{document}
\[ \begin{array}{l@{\,=\,}*{5}{l@{\,+\,}}l}
y_1 & x_{11} & x_{12} & x_{13} & \dots & x_{1(n-1)} & x_{1n} \\
y_2 & x_{21} & x_{22} & x_{23} & \dots & x_{2(n-1)} & x_{2n} \\
\ \vdots &\ \vdots &\ \vdots &\ \vdots &\ \ddots &\ \vdots &\ \vdots\\
y_{n-1} & x_{(n-1)1} & x_{(n-1)2} & x_{(n-1)3} & \dots & x_{(n-1)3} & x_{(n-1)n}\\
y_n & x_{n1} & x_{n2} & x_{n3} & \dots & x_{(n-1)(n-1)} & x_{nn}
\end{array} \]
\end{document}