%% 
%%  An UIT Edition example
%% 
%%  Example 09-16-7 on page 184.
%% 
%%  Copyright (C) 2010 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.
%% 
%% 
%% ==== 
% Show page(s) 1
%% 
\documentclass[]{exaarticle}
\pagestyle{empty}
\setlength\textwidth{375.57637pt}
\AtBeginDocument{\setlength\parindent{0pt}}
\setcounter{equation}{15}
\renewcommand\theequation{9.\arabic{equation}}
\StartShownPreambleCommands
\usepackage{gauss,fleqn}\renewcommand\rowmultlabel[1]{|\,\times#1}
\StopShownPreambleCommands
\begin{document}
\begin{equation}
  \begin{gmatrix}[p]
   1 &-2 & 1 & 2 \\ 2 & 3 &-2 & 3 \\ % rows 0 and 1
   4 &-1 & 3 &-1 \\ 3 & 2 &-4 & 5    % 2 and 3
  \rowops
  \mult{0}{(-2)} \add{0}{1} \mult{0}{(-4)}\add{0}{2} \mult{0}{(-3)} \add{0}{3}
  \end{gmatrix}
\end{equation}     % end matrix 1
\begin{equation}
  \begin{gmatrix}[p]
   1 &-2 & 1 & 2 \\ 0 & 7 &-4 &-1 \\% rows 0 and 1
   0 & 7 &-1 &-9 \\ 0 & 8 &-7 &-1   % 2 and 3
  \rowops
  \mult{1}{(-1)} \add{1}{2} \mult{1}{(-\frac{8}{7})} \add{1}{3}
  \end{gmatrix}
\end{equation}
\end{document}