[tex]\it A\cdot B=\left(\begin{array}{cc}6&-2\\ \\ 10&-3\end{array}\right) \cdot\left(\begin{array}{cc}-3&2\\ \\ -10&6\end{array}\right)=\left(\begin{array}{cc}2&0\\ \\ 0&2\end{array}\right)=2\cdot \left(\begin{array}{cc}1&0\\ \\ 0&1\end{array}\right)=2I_2[/tex]