Frequently asked questions - Math

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How do I align my equations at the equal sign?

Normally Math centers each line of a formula. To align each line at an equal sign you can use matrix, as shown in the following example.

Display Markup
 \begin{align} x + y &= 2 \\ x &= y-2 \end{align} matrix {
alignr x+y # {}={} # alignl 2 ##
alignr x # {}={} # alignl 2-y

The empty braces around the equal sign are necessary because = is a binary operator that needs an expression on each side.

The space around the = can be reduced by changing the spacing between columns of the matrix:

  • Select Format > Spacing.
  • Click Category and choose Matrices from the drop down menu.
  • Enter 0% for Column spacing.

Sometimes you need to "reserve" some space on the left of the equal sign in multi-line equations. Use phantom as shown below.

Header Display Markup
 \begin{align} 3(x+4)-2(x-1) &= 3 x+12-(2 x-2) \\  &= 3 x+12-2 x+2 \\ &= x+14 \end{align} ""3(x+4)-2(x-1)=3 x+12-(2 x-2) newline
""phantom {3(x+4)-2(x-1)}=3 x+12-2 x+2 newline
""phantom {3(x+4)-2(x-1)}=x+14

The phantom markup indicates that there should be a space the same length as "3(x+4)-2(x-1)". This results in the equal signs lining up properly.

Note: The "" can also be replaced with alignl.