Answer
$0$
Work Step by Step
The determinant of a $2 \times 2$ matrix can be computed by using the formula $det =ps-qr$
where $det =\begin{vmatrix}p & q \\r & s\end{vmatrix}$
$0 -1\begin{vmatrix} 2 & -1` \\4 & 2\end{vmatrix}+1 \begin{vmatrix} 2 &-1 \\ 4 & 2\end{vmatrix}=-[(4+4)+(4+4)]$
or, $=-8+8$
or, $=0$
