\documentclass[a4paper,11pt]{article}
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\usepackage[T1]{fontenc}
\usepackage{fourier}



\begin{document}

\begin{equation}
\label{eq:macierz:uzupelniona:przyklad}
U = \left[
\begin{array}{rrr|rr|r}
1 & 0 & 0 &  0 & -1 &  0\\
0 & 1 & 0 &  0 & -1 &  0\\
0 & 0 & 1 &  -3 & 0 & 0\\\hline
0 & 0 & \multicolumn{1}{r}{0} &  0 & 0 & 0\\
\end{array}
\right]
\end{equation}

\end{document}