# left align an alignedat environment

now I am trying to get this output aligned to the left of my document

This is the code that I am using to achieve it :

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{flalign*}
\begin{alignedat}{10}
&a &&\phantom{+ b} &&\phantom{+ c} &&\phantom{+ d} &&\phantom{+ e} &&\phantom{+ f} &&\phantom{+ g} &&\phantom{+ h} &&\phantom{+ i} &&= 0 \\
&\phantom{a} &&\phantom{+}b &&\phantom{+ c} &&+ d &&\phantom{+ e} &&\phantom{+ f} &&\phantom{+ g} &&\phantom{+ h} &&\phantom{+ i} &&= 0 \\
&\phantom{a} &&\phantom{+ b} &&\phantom{+} c &&\phantom{+ d} &&\phantom{+ e} &&\phantom{+ f} &&+ g &&\phantom{+ h} &&\phantom{+ i} &&= 0 \\
&\phantom{a} &&\phantom{+}b &&\phantom{+ c} &&+ d &&\phantom{+ e} &&\phantom{+ f} &&\phantom{+ g} &&\phantom{+ h} &&\phantom{+ i} &&= 0 \\
&\phantom{a} &&\phantom{+ b} &&\phantom{+ c} &&\phantom{+ d} &&\phantom{+} e &&\phantom{+ f} &&\phantom{+ g} &&\phantom{+ h} &&\phantom{+ i} &&= 0 \\
&\phantom{a} &&\phantom{+ b} &&\phantom{+ c} &&\phantom{+ d} &&\phantom{+ e} &&\phantom{+} f &&\phantom{+ g} &&+ h &&\phantom{+ i} &&= 0 \\
&\phantom{a} &&\phantom{+ b} &&\phantom{+} c &&\phantom{+ d} &&\phantom{+ e} &&\phantom{+ f} &&+ g &&\phantom{+ h} &&\phantom{+ i} &&= 0 \\
&\phantom{a} &&\phantom{+ b} &&\phantom{+ c} &&\phantom{+ d} &&\phantom{+ e} &&\phantom{+} f &&\phantom{+ g} &&+ h &&\phantom{+ i} &&= 0 \\
&\phantom{a} &&\phantom{+ b} &&\phantom{+ c} &&\phantom{+ d} &&\phantom{+ e} &&\phantom{+ f} &&\phantom{+ g} &&\phantom{+ h} &&\phantom{+} i &&= 0
\end{alignedat}
\end{flalign*}
\end{document}


This is what I am getting though :

Could you help me get it to the left of the page as desired?

Any help would be greatly appreciated, thanks in advance.

• Unrelated: ‘avec $0$ étant … is really bad style. Just write ‘$0$ étant …’. – Bernard Nov 18 '18 at 11:32

This doesn't use flalign but I hope that it helps!

\documentclass{article}
\begin{document}
$\begin{array}{cccccccccc} a & & & & & & & & &=0 \\ & b & &+\;d& & & & & &=0 \\ & & c & & & &+\;g& & &=0 \\ & b & &+\;d& & & & & &=0 \\ & & & & e & & & & &=0 \\ & & & & & f & &+\;h& &=0 \\ & & c & & & &+\;g& & &=0 \\ & & & & & f & &+\;h& &=0 \\ & & & & & & & & i &=0 \end{array}$
\end{document}


One advantage of this is that you can use it in the same line with your text (though I don't use that advantage usually).

• Wow, why was I giving myself so much trouble when this answer is simple yet so elegant 😊 thank you so much for that answer. – Sephya Nov 18 '18 at 5:54
• @Sephya: FYI, The correct binary operator spacing is given by {}+x, not +\;d. – Peter Grill Nov 18 '18 at 7:15
• @PeterGrill Thank you very much! I haven't heard of that before 😅 – JouleV Nov 18 '18 at 7:20
• @PeterGrill thanks for the tip, really appreciated – Sephya Nov 18 '18 at 8:24

You can easily left-align any display equations with the \fleqn environment from nccmath. An optional argument specifies at which distance the left margin the equations start (0pt by default).

I propose two solutions: one based on alignat*, with a simpler code, and another, with the systeme package – probably the simplest possible syntax:

\documentclass{article}
\usepackage[showframe]{geometry}
\usepackage{amsmath, nccmath}
\usepackage{systeme}

\begin{document}

\begin{fleqn}[\parindent]
\begin{alignat*}{10}
& a & \phantom{{}+{}} & &\phantom{{}+{}} & & & &\phantom{{}+{}}& &\phantom{{}+{}}& & & &\phantom{{}+{}} & &\phantom{{}+{}}& & & = 0 \\
& & & b & & & &+ d & & & & & & & & & & & & = 0 \\
& & & & & c & & & & & & & & + g & & & & & &= 0 \\
& & & b & & & &+ d & & & & & & & & & & & & = 0 \\
& & & & & & & & & e & & & & & & & & & & = 0 \\
& & & & & & & & & & & f & & & & + h & & & & = 0 \\
& & & & & c & & & & & & & & + g & & & & & & = 0 \\
& & & & & & & & & & & f & & & & + h & & & & = 0 \\
& & & & & & & & & & & & & & & & & & i & = 0
\end{alignat*}

\sysdelim..
\systeme{a = 0, \phantom{+}b + d = 0, \phantom{+}c + g = 0, b + d = 0, \phantom{+}e = 0, \phantom{+}f + h = 0, c + g = 0, f + h = 0, \phantom{+} i = 0}
\end{fleqn}

\end{document}


• FYI, I used to use the nccmath package package but ran into numerous issues that I decided to drop it. See Is there a replacement for nccmath? and the problems listed in the question. If all you want is the fleqn environment, you can use Stefan Kottwitz's solution from nccmath affecting minipage widths. – Peter Grill Nov 18 '18 at 17:14
• I personally never met a problem with nccmath, but I rarely use minipages. I use this package mainly for its medium-sized fractions (and formulæ, more generally) and its useful \useshortskip` command. – Bernard Nov 18 '18 at 17:20