# How to flush left centered part in multline environment?

I would like to use multline environment, but in that way that centered part be left aligned. With multline centered part is centered, and I would like if we can somehow to aligned it to the left (but to stay centered). And of course, if this is possible to do with align environment (but that first line is flush to left and last to the right), that is better for me, because than I can label arbitrary equations (because with multline I can label just last one equation). I hope I didn't confuse you too much.

Here you MWE

\documentclass{article}
\usepackage{amsmath,amssymb}
\usepackage{lipsum}

\begin{document}

\lipsum[1]

\begin{multline}
A = \lim _{n\rightarrow \infty }\Delta x\left( a^{2}+\left( a^{2}+2a\Delta x
+\left( \Delta x\right) ^{2}\right)\right.\\
+\left( a^{2}+2\cdot 2a\Delta x+2^{2}\left( \Delta x\right) ^{2}\right)\\
+\left( a^{2}+2\cdot 3a\Delta x+3^{2}\left( \Delta x\right) ^{2}\right)\\
+ \ldots\\
\left.+\left( a^{2}+2\cdot (n-1)a\Delta x +(n-1)^{2}\left( \Delta x\right) ^{2}\right) \right)\\
= \frac{1}{3}\left( b^{3}-a^{3}\right) + \text{something}
\end{multline}

\lipsum[2]

\end{document}


Perhaps you mean like this? (I used an subsidiary aligned for the inner alignment)

The code:

\documentclass{article}
\usepackage{amsmath,amssymb}
\usepackage{lipsum}

\begin{document}

\lipsum[1]

\begin{multline}
A = \lim _{n\rightarrow \infty }\Delta x\left( a^{2}+\left( a^{2}+2a\Delta x
+\left( \Delta x\right) ^{2}\right)\right.\\
\begin{aligned}
&+\left( a^{2}+2\cdot 2a\Delta x+2^{2}\left( \Delta x\right) ^{2}\right)\\
&+\left( a^{2}+2\cdot 3a\Delta x+3^{2}\left( \Delta x\right) ^{2}\right)\\
&+ \cdots\\
&+\left.\left( a^{2}+2\cdot (n-1)a\Delta x +(n-1)^{2}\left( \Delta x\right) ^{2}\right) \right)\\
\end{aligned} \\
= \frac{1}{3}\left( b^{3}-a^{3}\right) + \text{something}
\end{multline}

\lipsum[2]

\end{document}


Instead of \left, \right, use the \big, \bigg, family of commands as in

\documentclass{article}
\usepackage{amsmath,amssymb}
\usepackage{lipsum}

\begin{document}

\lipsum[1]

\begin{multline}
A = \lim _{n\rightarrow \infty }\Delta x \Bigl( a^{2}+\bigl( a^{2}+2a\Delta x
+ ( \Delta x ) ^{2}\bigr) \\
\begin{aligned}
&+ \bigl( a^{2}+2\cdot 2a\Delta x+2^{2} ( \Delta x ) ^{2} \bigr)\\
&+ \bigl( a^{2}+2\cdot 3a\Delta x+3^{2} ( \Delta x ) ^{2} \bigr)\\
&+ \cdots\\
&+\bigl( a^{2}+2\cdot (n-1)a\Delta x +(n-1)^{2} ( \Delta x ) ^{2} \bigr) \Bigr)\\
\end{aligned} \\
= \frac{1}{3} ( b^{3}-a^{3} ) + \text{something}
\end{multline}

\lipsum[2]

\end{document}


Even most of the parentheses can be safely removed.

• Yes, I wanted exactly that! "I used an subsidiary aligned for the inner alignmen" I didn't see that as solution. Thanks. Just one question: what If I want to label for example first, third and last equations. How to do that? – Cortizol Jul 19 '15 at 17:44
• "Instead of \left, \right, use the \big, \bigg, family of commands." Yes of course. I just copy/paste (and add \text{something}) example from here ctan.mirror.ac.za/info/math/voss/mathmode/Mathmode.pdf. – Cortizol Jul 19 '15 at 17:46
• @Cortizol I think that this new requirement qualifies for a new question since it has nothing to do with the alignment issue discussed here. In any case, for the required numbering I'm afraid you will have to abandon multline. – Gonzalo Medina Jul 19 '15 at 17:50
• Okay. I can ask new question (with link to this one), but for some reason, it can look like I am spamming if I ask two questions in 5 minutes. To wait one hour or maybe not? – Cortizol Jul 19 '15 at 17:55