Originally Posted by

**earboth** With Jonboy's method you can use different colours to cross out different terms.

$\displaystyle \frac{\bold{\rlap{{\color{red}====}}}(x + 5)(x - 2) \rlap{{\color{blue}---------}}(x + 7)}{\rlap{{\color{red}====}}(x + 5) \rlap{{\color{blue}---------}}(x + 7)} = \bold{x - 2}$

It would be nice and much more legible if the horizontal line could be printed in bold style. Unfortunately I didn't find the appropriate command

. The \bold{..} obviously only works with numbers and letters.

Using \vrule, you can create lines of any height, depth and width that you want. For example, $\displaystyle \frac{(\rlap{\color{red}\vrule height3.5pt depth-2pt width2.3em}x + 5)(x - 2) (\rlap{\color{blue}\vrule height3.5pt depth-2pt width2.3em}x + 7)}{(\rlap{\color{red}\vrule height3.5pt depth-2pt width2.3em}x + 5) (\rlap{\color{blue}\vrule height3.5pt depth-2pt width2.3em}x + 7)} = x - 2$ comes from this code:

Code:

\frac{(\rlap{\color{red}\vrule height3.5pt depth-2pt width2.3em}
x + 5)(x - 2) (\rlap{\color{blue}\vrule height3.5pt depth-2pt width2.3em}
x + 7)}{(\rlap{\color{red}\vrule height3.5pt depth-2pt width2.3em}
x + 5) (\rlap{\color{blue}\vrule height3.5pt depth-2pt width2.3em}
x + 7)} = x - 2