%%
%% The LaTeX Companion, 2ed (second printing August 2004)
%%
%% Example 8-7-7 on page 507.
%%
%% Copyright (C) 2004 Frank Mittelbach, Michel Goossens,
%%    Johannes Braams, David Carlisle, and Chris Rowley
%%
%% 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{183.0pt}

\StartShownPreambleCommands

\StopShownPreambleCommands
\begin{document}
\[
   \sqrt{ \frac{a+b}{x_j} }           \quad
   \sqrt{ \frac{a+b}{\smash{x_j}} }   \quad
   \sqrt{ \frac{a+b}{{}\smash{x_j}} } \quad
   \sqrt{ \frac{a+b}{\smash{x_j+b}} }
\]
\end{document}