# split inside flalign

I am currently using split inside the align environment similar to the following example

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\begin{align}
\begin{split}
a1 & = 3534534343 \\
a2 & = 2342342  \\
a3 & = 4564564  \\
a4 & = 5845645645864596464  \\
a5 & = 345354  \\
a6 & = 1
\end{split}
\end{align}
\end{document}


However I would like to have all these equations flushed to the left along with the property that there is single numbering for the system of equations (this is the reason for using the split). I can use the flalign environment without split but it gives numbering to all the individual equations

\documentclass{article}
\usepackage{amsmath}

\begin{document}

\begin{flalign}
a1 & = 3534534343 & \\
a2 & = 2342342  \\
a3 & = 4564564  \\
a4 & = 5845645645864596464  \\
a5 & = 345354  \\
a6 & = 1
\end{flalign}
\end{document}


I am unable to use the split inside flalign as it gives me an error. Is there an easy way to do this?

• If you are attempting to add more & inside the splitm, then no, split only allows up to one & per row. There is no build in inner companion for flalign like there is for align and gather. Perhaps you should try and explain exactly what it is you are trying to do and why you'll need flalign for that? I all the books I've setup I have never once used flalign. – daleif Aug 5 at 12:35
• I want to have a single numbering for all the equations. Is there a way to do it other than split? I just want everything the same as the first MWE just all the equations to the left instead of centered. – Siddhant Aug 5 at 12:38
• But why flalign? IMO it is much less readable than align – daleif Aug 5 at 12:46
• How else can I flush a set of aligned equations to the left? I actually hate using the flalign environment and really like the align environment but I dont know how to flush all these equations on the left within align – Siddhant Aug 5 at 12:48
• Other display formulas in the document should remain centered and only this one set flush left, or is it that you'd like to have all display formulas flush left? – frougon Aug 5 at 12:54

It is not very clear what you like to achieve, but the following solution may help you:

\documentclass{article}
\usepackage{nccmath}

\usepackage{lipsum}

\begin{document}
\lipsum[11]
\begin{fleqn} % defined in nccmath
$$\begin{split} a1 & = 3534534343 \\ a2 & = 2342342 \\ a3 & = 4564564 \\ a4 & = 5845645645864596464 \\ a5 & = 345354 \\ a6 & = 1 \end{split}$$
\end{fleqn}
\lipsum[12]
$c^2 = a^2 + b^2$
\end{document}


Environment \begin{flegn} ... \end{fleqn} (defined in nccmath package) locally align equation to the left (as do amsmath option fleqn for whole document).

• Thanks! I didn't know that fleqn was so flexible. I can even use align within fleqn – Siddhant Aug 5 at 13:19
• +1. :-) About your earlier answer that involved \hdotfill: I apologize profusely for not being much clearer. I was actually offering to delete my answer if you wanted to take its main ideas on board yourself. So sorry for not being sufficiently. Please reconsider your delete decision. – Mico Aug 5 at 14:11
• @Mico, I know, and it is ok. I'm on vacation (and my brain too ;-) so I'm very relaxing (read lazy) now, so I look site not very serious, when other member of family have siesta :-) – Zarko Aug 5 at 14:22
• @Zarko - By all means, have a wonderful, relaxing summer vacation. – Mico Aug 5 at 14:29
• @Zarko happy vacations btw! – manooooh Aug 5 at 16:19

You should be aware that flalign stands for full length align and not for flush left align.

As such, split doesn't really make sense inside it.

You can emulate split using aligned.

\documentclass{article}
\usepackage{amsmath}

\usepackage{lipsum} % for mock text

\begin{document}

\lipsum[1][1-3]
\begin{flalign}
\begin{aligned}
a1 & = 3534534343 \\
a2 & = 2342342  \\
a3 & = 4564564  \\
a4 & = 5845645645864596464  \\
a5 & = 345354  \\
a6 & = 1
\end{aligned}&&
\end{flalign}
\lipsum[2][1-3]

\end{document}
`

On the other hand, I see no reason for some displays to be flush left and others centered.

• Off-topic. First time I see a bold italized text from one of your answers. Glad to see it! – manooooh Aug 5 at 16:21