How-to

How to Write a System of Equations in LaTeX

The fix

To write a system of equations in LaTeX, load \usepackage{amsmath}. For a single left brace grouping several equations, use the cases environment; for several separately numbered equations aligned at the equals sign, use align. Align at & and end rows with \\.

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Example

\usepackage{amsmath}
% Braced system:
\[
\begin{cases}
  x + y = 2 \\
  x - y = 0
\end{cases}
\]
% Aligned and numbered:
\begin{align}
  2x + y &= 5 \\
  x - 3y &= -2
\end{align}

Frequently asked questions

How do I get a left brace around the system?

Use the cases environment from amsmath. It draws the brace automatically. For a taller custom brace, use \left\{ ... \right. around an array.

Should I use align or cases?

Use cases for one braced group presented as a set; use align when each equation should sit on its own line, aligned at = and individually numbered.

Related LaTeX fixes

How-toAlign equationsHow-toPiecewise / casesErrorEnvironment undefinedHow-toBold text

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