127

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

\[
    a + b = c // what should I add here?
    a = c - b
\]
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3 Answers 3

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136

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:

enter image description here

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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5
  • 1
    I tried align, it shows everything on the same line. My code: pastebin.com/FwwSmiCp Result: image description
    – Tomáš Zato
    Jan 16, 2017 at 9:46
  • 3
    @TomášZato: You need a double back slash to indicate a new line, not a single backslash. Next time, for faster response, just post a new question. You won't be the last person to make such a mistake -- even if it gets closed, the comments will still contain a fix, so a question like that might help someone else in the future. I see that there is a typo in my answer, so fixing that now...
    – Peter Grill
    Jan 16, 2017 at 22:58
  • As of January 9th, your link to Herbert Voss's eview of LaTeX math is dead.
    – IdleCustard
    Jan 9, 2019 at 16:07
  • with align, I'm getting equation numbers next to each line. I preferred this answer to a similar question: tex.stackexchange.com/a/8942/14277
    – craq
    Jul 29, 2019 at 22:55
  • @craq: Glad you were able to locate a solution for your issue. However, this question is about adding a line break between equations, not about splitting a single equation across multiple lines.
    – Peter Grill
    Jul 30, 2019 at 0:25
7

In case gather is not an option, for example, an imported command where everything is in math mode, consider make them a single-columned matrix without showing the symbol, then you can use \\.
Code:

\[
\begin{array}{c}
a + b = c \\  % just use \\
a = c - b
\end{array}
\]
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1
  • This solution works, but it might be important to keep in mind that in an array environment, the content is (by default) in \textstyle rather than in \displaystyle. Hence, for example, a fraction written with \frac{}{} will be smaller than in an usual display math environment, and the limits of a sum or of an integral will be displayed differently. But one could simply add a \displaystyle command in cells where this behavior should be changed.
    – Vincent
    Mar 28, 2020 at 21:50
1

Why not use two modes.

\[
    a + b = c
\]
\[
    a = c - b
\]
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1
  • 7
    There will be too much space between the two lines, and also the possibility of a page break. Not a good choice.
    – barbara beeton
    Jun 24, 2021 at 1:50

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