split inside flalign

Question

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?

Answer 1

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

Answer 2

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.