## College Algebra (6th Edition)

$AB=\left[\begin{array}{ll} 0 & -1\\ 1 & 0 \end{array}\right]\left[\begin{array}{ll} 1 & 0\\ 0 & -1 \end{array}\right]$ $=\left[\begin{array}{ll} 0+0 & 0+1\\ 1+0 & 0+0 \end{array}\right]=\left[\begin{array}{ll} 0 & 1\\ 1 & 0 \end{array}\right]$ $BA=\left[\begin{array}{ll} 1 & 0\\ 0 & -1 \end{array}\right]\left[\begin{array}{ll} 0 & -1\\ 1 & 0 \end{array}\right]$ $=\left[\begin{array}{ll} 0+0 & -1+0\\ 0-1 & 0+0 \end{array}\right]=\left[\begin{array}{ll} 0 & -1\\ -1 & 0 \end{array}\right]=-AB$ $AB=-BA$ so A and B are anticommutative.