We have the following matrix :

$\displaystyle A=\begin{pmatrix} 2 &0&0 \\ 0&0&1 \\ 0&-1&0 \end{pmatrix}$

How can I found a triangle matrix similar to the initial matrix.

I was pleased if someone show me the step by step solution because I have 2 more matrices to do exactly the same procedure.

Thanks in Advance