[tex]A=\left[\begin{array}{ccc}3&0\\1&-4\end{array}\right][/tex] [tex]B=\left[\begin{array}{ccc}2&1\\-1&0\end{array}\right][/tex]
[tex]A.B=\left[\begin{array}{ccc}3.2+0.(-1)&3.1+0.0\\1.2+(-4).(-1)&1.1+(-4).0\end{array}\right]=\left[\begin{array}{ccc}6+0&3+0\\2+4&1+0\end{array}\right]=\left[\begin{array}{ccc}6&3\\6&1\end{array}\right][/tex]
[tex]B.A=\left[\begin{array}{ccc}2.3+1.1&2.0+1.(-4)\\(-1).3+0.1&(-1).0+0.(-4)\end{array}\right]=\left[\begin{array}{ccc}6+1&0-4\\-3+0&0+0\end{array}\right]=\left[\begin{array}{ccc}7&-4\\-3&0\end{array}\right][/tex]
[tex]AB-BA=\left[\begin{array}{ccc}6&3\\6&1\end{array}\right]-\left[\begin{array}{ccc}7&-4\\-3&0\end{array}\right]=\left[\begin{array}{ccc}6-7&3-(-4)\\6-(-3)&1-0\end{array}\right]=\left[\begin{array}{ccc}-1&7\\9&1\end{array}\right][/tex]
