# [texhax] hline or underline in align environment

E. Krishnan ekmath at asianetindia.com
Tue May 3 03:41:58 CEST 2005

On Sun, 1 May 2005, John Wheeler wrote:

> I'm using the align environment (having gratefully graduated from eqnarray
> at the suggestion of this group) and need to be able to put an underline
> beneath one equation before proceeding to the next, as in adding two
> equations to obtain a third.

Two possible solutions might be

1. \usepackage{amsmath}

\begin{equation*}
\renewcommand{\arraystretch}{1.1}
\begin{matrix}
2x^2 & - & 3x & + & 4\\
&   & 2x & + & 1\\
\hline
2x^2 & - &  x & + & 5
\end{matrix}
\end{equation*}

2. \usepackage{array}

\newcolumntype{M}{>{$}c<{$}}
{\renewcommand{\arraystretch}{1.1}
\begin{tabular}{*{5}{@{\:}M}}
2x^2 & - & 3x & + & 4\\
&   & 2x & + & 1\\
\hline
2x^2 & - &  x & + & 5
\end{tabular}}

--
Krishnan