$$$\left[\begin{array}{cc}3 & 11\\1 & 12\end{array}\right]$$$ 的行列式

計算 $$$\left|\begin{array}{cc}3 & 11\\1 & 12\end{array}\right|$$$。

2x2 矩陣的行列式為 $$$\left|\begin{array}{cc}a & b\\c & d\end{array}\right| = a d - b c$$$。

$$$\left|\begin{array}{cc}3 & 11\\1 & 12\end{array}\right| = \left(3\right)\cdot \left(12\right) - \left(11\right)\cdot \left(1\right) = 25$$$

$$$\left|\begin{array}{cc}3 & 11\\1 & 12\end{array}\right| = 25$$$A