## Precalculus (10th Edition)

$4$
RECALL: $\begin{vmatrix} a & b \\ c & d \end{vmatrix}=ad-bc$ Use the definition above to obtain $\begin{vmatrix} 6 & 5 \\ -2 & -1 \end{vmatrix}=6(-1)-5(-2)=-6+10=4$