计算行列式 $\left|\begin{array}{cccc}
-1 & -1 & -1 & -1 \\
-1 & -1 & -1 & 1 \\
-1 & -1 & 1 & 1 \\
-1 & 1 & 1 & 1
\end{array}\right|$
计算 $\left|\begin{array}{cccc}
1 & b_1 & 0 & 0 \\
-1 & 1-b_1 & b_2 & 0 \\
0 & -1 & 1-b_2 & b_3 \\
0 & 0 & -1 & 1-b_3
\end{array}\right|=$
计算$\left|\begin{array}{cccc}
-a_1 & 0 & 0 & 1 \\
a_1 & -a_2 & 0 & 1 \\
0 & a_2 & -a_3 & 1 \\
0 & 0 & a_3 & 1
\end{array}\right|=$
已知方程 $\left|\begin{array}{ccc}x-2 & 0 & 0 \\ -3 & x-1 & a \\ 2 & a & x-1\end{array}\right|=0$ 有二重根, 求满足条件的常数 $a$ 及方程的根.
设 $A =\left[ \alpha _1, \alpha _2, \alpha _3\right]$ 是 3 阶矩阵, 且 $| A |=4$, 若
$$
B =\left[ \alpha _1-3 \alpha _2+2 \alpha _3, \alpha _2-2 \alpha _3, 2 \alpha _2+ \alpha _3\right],
$$
则 $| B |=$