4 1 2 4 1 2 0 2 1 2 0 2 1 2 0 2 1 2 0 2
1 2 0 2 = 4 1 2 4 = 0 -7 2 -4 = 0 1 1 7 = 0 1 1 7
10 5 2 0 10 5 2 0 0 -15 2 -20 0 -15 2 -20 0 0 17 85
0 1 1 7 0 1 1 7 0 1 1 7 0-7 2 -4 0 0 9 45
1 2 0 2
=0 1 1 7 =1*1*17*0=0
0 0 17 85
0 0 0 0
每一行四个一组写进行列式,原则是把它化为上三角形