%% 
%%  Der Mathematiksatz mit LaTeX, 1. Auflage 2009
%% 
%%  Example 6-2-4 on page 87.
%% 
%%  Copyright (C) 2009 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.
%% 

\documentclass[]{ttctexa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{170.59192pt}
\AtBeginDocument{\setlength\parindent{0pt}
\setlength\abovedisplayskip{-10pt}
\setlength\belowdisplayskip{-10pt}}
\StartShownPreambleCommands
\usepackage{amsmath}
\StopShownPreambleCommands
\begin{document}
\begin{align*}  y &= x   \end{align*}
\begin{align*}  y =& x   \end{align*}
\begin{align*}  y ={}& x \end{align*}
\end{document}