# Number only some equations in an equation array

I have an equation array consisting of around 9 equations, however I wish to number only some of them. How can I do that?

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You can use \nonumber before the \\. –  azetina Oct 17 '12 at 13:54
–  azetina Oct 17 '12 at 13:55

You can use \notag and/or \nonumber from amsmath (or improvised mathtools package):

\documentclass{article}
\usepackage{mathtools,amssymb}

\begin{document}
\begin{align}
x &= y \\\nonumber
x &= 3 \\
y &= 10 \\ \notag
\therefore\ x &\neq y \\
x &= y \\\nonumber
x &= 3 \\
y &= 10 \\ \notag
\therefore\ x &\neq y \\
? &=?
\end{align}
\end{document}


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