%%
%% The LaTeX Companion, 3ed
%%
%% Example 5-6-4 on page I-418 in "addlines --- Adjusting whole double spreads".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3exa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{126.00128pt}

  \setlength\textheight{10.3\baselineskip}
  \addtolength\footskip{-6pt}

  \tolerance=4000

  \pagestyle{origplain}
  \flushbottom

%StartShownPreambleCommands
\usepackage{lipsum,addlines}
\flushbottom
%StopShownPreambleCommands

\begin{document}
\lipsum[1][1] \[ \sum x_i \]
\squeezepage[1]
\lipsum[1][2] \[ \sum y_i \]
Now will this final paragraph
still fit in its entirety on
the page? \par
\lipsum[1][1] \[ \sum x_i \]
\lipsum[1][2] \[ \sum y_i \]
Now will this final paragraph
still fit in its entirety on
the page?
\end{document}