[a00−a]\left[\begin{array}{cc}a & 0 \\0 & -a\end{array}\right][a00−a]
[a0−a0]\left[\begin{array}{rr}a & 0 \\-a & 0\end{array}\right][a−a00]
[0a−a0]\left[\begin{array}{cc}0 & \mathbf{a} \\-a & 0\end{array}\right][0−aa0]
[0−a0a]\left[\begin{array}{cc}0 & -a \\0 & a\end{array}\right][00−aa]
