# Leftalign, align and have only one number

I have an equation that I want to leftalign. Also I needed to split this equation due to its length and since we are talking only about one equation, I want to give this equation only one number, not one in each row.

I created this minimal example

 \begin{flalign*}
\lambda &= \lambda_1 + \lambda_2 &\\
&= \Lambda &\\
&= \Lambda_1 + \Lambda_2 &
\end{flalign*}


This does the first two things leftalign and align, but here each row gets a number, how can I change this?

• put \nonumber or (\notag) before \\  where you don't want number. – user11232 Feb 27 '15 at 1:55
• do you want all your display math flush left? if so, there is another way, with better results for a display with an even number of lines. – barbara beeton Feb 27 '15 at 14:33

You can use \nonumber (or \notag) or aligned as below.

\documentclass{article}
\usepackage{amsmath}
\usepackage{showframe}  %% for demo

\begin{document}
\begin{flalign}
\lambda &= \lambda_1 + \lambda_2 &\notag\\
&= \Lambda &\\
&= \Lambda_1 + \Lambda_2 & \notag
\end{flalign}
\begin{flalign}
&\!\begin{aligned}
\lambda &= \lambda_1 + \lambda_2 &\\
&= \Lambda &\\
&= \Lambda_1 + \Lambda_2 &
\end{aligned}&
\end{flalign}
\end{document}