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\documentclass{article}
\usepackage{amsmath}
\makeatletter
\renewcommand*\env@matrix[1][*\c@MaxMatrixCols c]{%
  \hskip -\arraycolsep
  \let\@ifnextchar\new@ifnextchar
  \array{#1}}
\makeatother
\begin{document}
\begin{equation}
  \begin{bmatrix}[cc|c|c]
0 & -I & I & 0\\
0 & 0 & -I & I \\
\end{bmatrix}
\end{equation}
\end{document}

enter image description here

2
  • Is your image the matrix you want? Or the matrix you get? What does your code snippet do? Could you make it a complete example by including the necessary \usepackage and document commands?
    – Teepeemm
    Sep 29, 2020 at 17:00
  • here you go, i modified it. i was just able to generate like the right matrix in the picture but i need the left one.
    – user224189
    Sep 29, 2020 at 17:06

1 Answer 1

2

You can't get those matrices just with bmatrix, but you need to use the lower level array:

\documentclass{article}
\usepackage{amsmath,booktabs}

\begin{document}

\[
\mathbf{L}=
\begin{bmatrix}
\begin{array}{@{}cc@{}}
\mathbf{I} & \mathbf{0} \\
\mathbf{0} & \mathbf{I} \\
\midrule[\arrayrulewidth]
\mathbf{0} & \mathbf{I} \\
\midrule[\arrayrulewidth]
\mathbf{0} & \mathbf{I}
\end{array}
\end{bmatrix}
\implies
\mathbf{L}^+=
\begin{bmatrix}
\begin{array}{@{}cc|c|c@{}}
\mathbf{I} & \mathbf{0} & \mathbf{0} & \mathbf{0} \\
\mathbf{0} & \mathbf{I} & \mathbf{0} & \mathbf{0}
\end{array}
\end{bmatrix}
\]

\end{document}

enter image description here

2
  • when i adding ` \begin{equation}` ` \end{equation}` does not work. it seems not possible to put in one equation.
    – user224189
    Sep 29, 2020 at 20:06
  • @user224189 You need to replace \[ with \begin{equation} and \] with \end{equation}.
    – egreg
    Sep 29, 2020 at 20:17

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