[tex] \left[\begin{array}{ccc}1&2&0\\3&-1&2\end{array}\right] . \left[\begin{array}{ccc}2&0&\\1&-3\\-1&2\end{array}\right] =[/tex]
[tex] \left[\begin{array}{ccc}2+2+0&0+6+0\\6-1-2&0+3+4\end{array}\right] =[/tex]
[tex] \left[\begin{array}{ccc}4&6\\3&7\end{array}\right] [/tex]
lembrando que a multiplicação de matrizes e da horizontal pela a vertical.
se for pra resolver e assim.