Answer
$0$
Work Step by Step
The determinant $D$ of a $ 2 \times 2$ matrix can be calculated as:
$D=\left|\begin{array}{ll}
A & B\\C & D \end{array}\right|=AD-BC$
The determinant $D$ of a given $ 2 \times 2$ matrix can be calculated as:
$D=\left|\begin{array}{ll}
9 &3\\ -3 & -1 \end{array}\right|=(9)(-1)-(3)(-3)=-9+9=0$
