第2行乘 -1 加到其余各行-1 0 0 ...0 2 2 2 ...20 0 1 ...0......0 0 0 ...n-2第2列乘 -1 加到其余各列-1 0 0 ...0 0 2 0 ...00 0 1 ...0......0 0 0 ...n-2行列式 = (-1)2(n-1)!= -2(n-2)!