# How do I left-align this equation?

I wrote an equation in LaTeX, and it is centered. How can I left align it but without losing the split? (I still want the equal signs one under each other).

Code:

\begin{equation*}
\begin{split}
a &=(3+6+9+12+...+147)+1125\\
&=3 \cdot (1+2+3+4+...+49)+1125\\
&=3 \cdot \displaystyle\frac{49 \cdot 50}{2} + 1125=49 \cdot 75 + 1125\\
&=3675 + 1125\\
&=4900\\
&=70^2 \Rightarrow \sqrt{a} = \sqrt{70^2}=70 \end{split}
\end{equation*}

• Juste celle-ci à gauche, ou toutes vos équations? – Bernard May 13 '17 at 13:57
• Does the fleqn option to the documentclass help? – Andrew Swann May 13 '17 at 13:59
• You can replace \begin{equation*}\begin{split} with \begin{flalign*} and add & before every \\  as a quick fix. Although I'd also change some other aspects of your euation, such as multiple equal signs on some lines, which makes things messy IMO. Also, ... should be replace with \ldots. – hooy May 13 '17 at 14:04
• For an occasional left-aligned equation , the fleqn environment from nccmath does the job. – Bernard May 13 '17 at 14:14
• The main question is: why should the display be left aligned? – egreg May 13 '17 at 19:59

I find no reason for this display to be flush left. Anyway…

\documentclass{article}
\usepackage{amsmath}

\begin{document}

The following display is left aligned. I don't know why it should be
treated differently from the other displays, but here it is anyhow.
\begin{flushleft}
\begin{aligned} a &=(3+6+9+12+\dots+147)+1125\\ &=3 \cdot (1+2+3+4+\dots+49)+1125\\ &=3 \cdot \frac{49 \cdot 50}{2} + 1125=49 \cdot 75 + 1125\\ &=3675 + 1125\\ &=4900\\ &=70^2 \Rightarrow \sqrt{a} = \sqrt{70^2}=70 \end{aligned}
\end{flushleft}
Note that dots should be specified with \verb|\dots|, not with
three periods and that \verb|\displaystyle| is not needed; there
is \verb|\dfrac|, if needed (not here).

\end{document}


I'm not sure if this is exactly what you want, but you could use \parbox with the width set to 0 to accomplish this.

\noindent Previous line.

\noindent\parbox{0mm}{
\begin{equation*}
\begin{split}
a &=(3+6+9+12+...+147)+1125\\
&=3 \cdot (1+2+3+4+...+49)+1125\\
&=3 \cdot \displaystyle\frac{49 \cdot 50}{2} + 1125=49 \cdot 75 +
1125\\
&=3675 + 1125\\
&=4900\\
&=70^2 \Rightarrow \sqrt{a} = \sqrt{70^2}=70 \end{split}
\end{equation*}
}

\noindent Next line.