This is LaTeX code:
[latex]
A = \left [ \begin{array}{c c c c} 1 & 0 & 0 & 0 \\ 2 & 1 & 0 & 0 \\ -3 & 4 & 1 & 0 \\ 1 & -1 & 0 & 1 \\ \end{array} \right ]
[/latex]