%% 
%%  Ein Beispiel der DANTE-Edition
%%  Mathematiksatz mit LaTeX
%%  3. Auflage
%%  Beispiel 06-02-5 auf Seite 89.
%%  Copyright (C) 2018 Herbert Voss
%% 
%%  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.
%%  See http://www.latex-project.org/lppl.txt for details.
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\documentclass[10pt]{screxa}
\pagestyle{empty}
\setlength\textwidth{194.40707pt}
\AtBeginDocument{\setlength\parindent{0pt}}
\setcounter{equation}{0}
\renewcommand\theequation{6.\arabic{equation}}
%StartShownPreambleCommands
\usepackage{amsmath}
%StopShownPreambleCommands
\begin{document}
\begin{align}
 y      &= d\\
 y      &= cx+d\\
 y_{12} &= bx^2+cx+d\\
 y(x)   &= ax^3+bx^2+cx+d
\end{align}
\end{document}