# Align matrix to be flush left with delimiter in 'align'

I'm using amsmath and matrices in the align environment and can't get the text at the end of a line to be flush left.I would like the matrices on the right to be flush with the matrices on the left and not the right margins.

\documentclass[oneside,letterpaper,11pt]{report}
\usepackage{mathtools}

\begin{document}

\begin{align*}
\begin{bmatrix}
2  &  2  &  0  &  0  &  2 & -2 \\
13 &  13 &  -3 &  -6 &  4 & 2 \\
-9 &  -9 &  1  &  2  &  -6& 4 \\
\end{bmatrix}
\begin{bmatrix}
1  &  1  &  0  &  0  &  1 & -1 \\
13 &  13 &  -3 &  -6 &  4 & 2 \\
-9 &  -9 &  1  &  2  &  -6& 4 \\
\end{bmatrix} \\
\begin{bmatrix}
1  &  1  &  0  &  0  &  1 & -1 \\
0  &  0  &  -3 &  -6 &  -9& -11  \\
-9 &  -9 &  1  &  2  &  -6& 4 \\
\end{bmatrix}
\begin{bmatrix}
1  &  1  &  0  &  0  &  1 & -1 \\
0  &  0  &  -3 &  -6 &  -9& -11  \\
0  &  0  &  1  &  2  &  3& -5 \\
\end{bmatrix}\\
\end{align*}

\end{document}

• Welcome to TeX.SX. When you write "flush with the arrows", do you get the effect you want by deleting the & after the \rightarrow? You could add a \quad space to keep symmetry. Also, it is good form to include a complete "Minimal Working Example" (MWE) that starts with \documentclass, includes all relevant \usepackage commands, ends with \end{document} and compiles without errors, even if it does not produce your desired output. – Sandy G Nov 20 '17 at 4:23
• Updated the code per requirements and changed delimiters from your suggestion. The effect minimizes the results in the sample code but does not solve the issue. – Patrick Nov 20 '17 at 4:50
• Still too many &s. Delete the & after the = in the first row after \begin{flalign*}. Then delete both &s in the first line with \rightarrow. Then delete the & after the \rightarrow before the 3rd matrix, and delete both &s around the \rightarrow before the 4th matrix. Lastly, don't leave math mode so much. Your code $R_1$ $\div$ $2$ $\rightarrow$ $R_1$ should be $R_1\div 2 \rightarrow R_1$. – Sandy G Nov 20 '17 at 5:04

Maybe this?

\documentclass[oneside,letterpaper,11pt]{report}
\usepackage{mathtools}

\makeatletter
\renewcommand*\env@matrix[1][c]{
\edef\arraystretch{1.25}%
\hskip -\arraycolsep
\let\@ifnextchar\new@ifnextchar
\array{*\c@MaxMatrixCols #1}}
\makeatother

\begin{document}

\begin{flalign*}
\begin{bmatrix}[r]
2  &  2  &  0  &  0  &  2 & -2 \\
13 &  13 &  -3 &  -6 &  4 & 2 \\
-9 &  -9 &  1  &  2  &  -6& 4 \\
\end{bmatrix}
\stackrel{\mbox{$R_1 \div 2 \rightarrow R_1$}}{
\begin{bmatrix}[r]
1  &  1  &  0  &  0  &  1 & -1 \\
13 &  13 &  -3 &  -6 &  4 & 2 \\
-9 &  -9 &  1  &  2  &  -6& 4 \\
\end{bmatrix}} &\\[1.5em]
\stackrel{\mbox{$R_2 - 13R_1\rightarrow R_2$}}{
\begin{bmatrix}[r]
1  &  1  &  0  &  0  &  1 & -1 \\
0  &  0  &  -3 &  -6 &  -9& -11  \\
-9 &  -9 &  1  &  2  &  -6& 4 \\
\end{bmatrix}}
\stackrel{\mbox{$R_3 + 9R_1\rightarrow R_2$}}{