Zdroj TeX:

\small \left(\begin{array}{rrr}1&-2&1\\1&1&-1\\-2&0&1\\ \end{array}\right) \cdot \left(\begin{array}{ccc} 5 \\ -1 \\ 9 \end{array}\right) = \left(\begin{array}{ccc} r \\ s \\ t \end{array}\right)