%% 
%%  Ein Beispiel der DANTE-Edition
%%  Mathematiksatz mit LaTeX
%%  3. Auflage
%%  Beispiel 06-11-1 auf Seite 112.
%%  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.
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[10pt]{screxa}
\pagestyle{empty}
\setlength\textwidth{352.81416pt}
\AtBeginDocument{\setlength\parindent{0pt}
\setcounter{equation}{50}
\renewcommand\theequation{\arabic{equation}}}
\usepackage{blkarray}
\newcommand\bigstrutht{\vrule width0pt height 12pt depth0pt\relax}
\newcommand\bigstrutdp{\vrule width0pt height 0pt depth5pt\relax}
%StartShownPreambleCommands
\usepackage{amsmath,blkarray}
\renewcommand\theequation{\arabic{equation}}
%StopShownPreambleCommands
\begin{document}
\begin{align}\begin{blockarray}{*{4}{c}}
  \begin{block}{[ccc]c}
    \bigstrutht 1-\lambda x & 0 & 0 & \ell_1 \\  0 & 1-\lambda x & 0 & \ell_2 \\
    \bigstrutdp 0 & 0 & 1-\lambda x & \ell_3 \\
  \end{block}
  c_1 & c_2 & c_3
\end{blockarray}\end{align}
\end{document}