[texhax] hline or underline in align environment

[E. Krishnan]

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}
      \addtolength{\arraycolsep}{-3.5pt}
      \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