## Algebra and Trigonometry 10th Edition

$-4$
The general form of a matrix of order $2 \times 2$ is: $det \ A=\begin{bmatrix} p & q \\ r & s\end{bmatrix}=ps-qr$ Since Column-1 has the most zeroes, we choose Column-1. It has sign array $(+,+)$ as we go down. Now, $det \ A =0+0+(-1) \begin{bmatrix} 1 & -2 \\ 1 & 2 \end{bmatrix}=-1(2+2)=-4$