## Differential Equations and Linear Algebra (4th Edition)

$29$
For any matrix $\left[ {\begin{array}{cc} a & b \\ c & d \\ \end{array} } \right]$ the determinant equals $ad-bc$. For the matrix $\left[ {\begin{array}{cc} 9 & -8 \\ -7 & -3 \\ \end{array} } \right]$ the determinant equals $9(-3)-(-7)(-8)=29.$