# An underbracket in a matrix

Good evening

I would like to get two brackets below a matrix (the picture below).

Thank you for help.

• also good Sunday evening! do you try anything? please show this. – Zarko Oct 2 '16 at 17:58
• No. I'm writing my maths notes to school. :) Can you help me? – Ľubomír Masarovič Oct 2 '16 at 17:59
• It might be the simplest way to draw this matrix with help of tikz package and matrix library. See TikZ & and PGF manual, chapters 20 (Matrices and Alignment, page 305) and 57 (Matrix Library, page 646). There are lot of examples. If you will stuck in your effort to solve your problem yourself, people here will more willing to help you. – Zarko Oct 2 '16 at 18:08

If you don't have many of these structures, you can do as follows: in the argument to \underbrace you repeat the part of the matrix the brace refers to.

\documentclass{article}
\usepackage{amsmath}
\usepackage{lipsum}

\begin{document}

\lipsum*[2]
\begin{equation*}
A=
\begin{gathered}[t]
\left(\begin{array}{ccc|cc}
1 & 2 & 3 & 4 & 5 \\
11 & 2 & 3 & 44 & 5
\end{array}\right)
\\[-\normalbaselineskip]
\underbrace{\hphantom{%
\begin{array}{@{}ccc@{}}
1 & 2 & 3 \\
11 & 2 & 3
\end{array}%
}}_{\text{some text}}
\hspace{2\arraycolsep}\hspace{\arrayrulewidth}
\underbrace{\hphantom{%
\begin{array}{@{}cc@{}}
4 & 5 \\
44 & 5
\end{array}%
}}_{\text{text}}
\end{gathered}
\end{equation*}
\lipsum[3]

\end{document}