Exercise 4.4.32

$Q_1=\left[\begin{array}{cc}\hfill 1& \hfill 0\\ \hfill 0& \hfill -1\end{array}\right]$reflects across $x$ axis, $Q_2=\left[\begin{array}{ccc}\hfill 1& \hfill 0& \hfill 0\\ \hfill 0& \hfill 0& \hfill -1\\ \hfill 0& \hfill -1& \hfill 0\end{array}\right]$across plane $y+z=0$.