\left[ \matrix{%
1&2&-1\cr
3&0&2}\right] \cdot
\left[ \matrix{%
2&1\cr
-2&1\cr
1&3}\right] =
\left[ \matrix{%
2-4-1&1+2-3\cr
6+0+2&3+0+6}\right] = 
\left[ \matrix{%
-3&0\cr
8&9}\right]