# How do I add a line break in display math mode?

For instance, how do I add a break after the first line in

$a + b = c // what should I add here? a = c - b$
-

The $...$ is used to typeset a single equation, not multiple equations.

You need to use an environment that allows for multiple equations. One way is to use gather, but I normally use align, both from the amsmath package:

## Notes:

• With display math environments if you leave blank lines in between you get additional vertical spacing and the possibility of a page break between a paragraph and following display.
• If you don't want the equations numbered use the starred versions of the environments: gather* and align*.
• A really good reference is Herbert Voss's comprehensive review of mathematics in (La)TeX.

## Code:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{gather}
a + b = c \\
a = c - b
\end{gather}
%
With the align environment you can align equations:
%
\begin{align}
a + b &= c \\
a &= c - b
\end{align}
\end{document}
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should there be a blank line immediately before your align environment? –  cmhughes Feb 29 '12 at 3:19
@cmhughes: Thanks. Have corrected and made a note of it in the solution. –  Peter Grill Feb 29 '12 at 3:35