Aligning equations

Lining equations up

• When you show working, readers like the = signs to line up. The align* environment does this:

\begin{align*}
  y &= 2(x + 3) \\
  y &= 2x + 6
\end{align*}

• The & marks where to align (just before each =), and \\ ends each line.

Numbered or not

• align* (with the star) gives no equation numbers.
• Drop the star — align — and LaTeX numbers each line (1), (2), … for you to refer to.

Matrices

• amsmath also gives matrices. bmatrix draws square brackets:

\[
  \begin{bmatrix} 1 & 2 \\ 3 & 4 \end{bmatrix}
\]

• Again & separates columns and \\ separates rows — the same idea as alignment.

Common mistakes

• align without amsmath. LaTeX stops with ! LaTeX Error: Environment align undefined.
• A blank line inside align. It gives ! Paragraph ended before \align was complete. Keep the lines together; \\ already starts a new row.
• The & in different places. Put it just before the symbol to line up, usually &=, on every line.