Question

If $A=\left[\begin{array}{cc}1& 2\\ 3& 4\end{array}\right]$, find $|2A|$.

Answer 1

$A=\left[\begin{array}{cc}1& 2\\ 3& 4\end{array}\right]$

$2A=\left[\begin{array}{cc}2& 4\\ 6& 8\end{array}\right]$

$|2A|=16-24=-8$