2 1 -5 8 1 -3 0 9 0 2 -1 -5 1 4 -7 0 答案等于27,

题目

2 1 -5 8 1 -3 0 9 0 2 -1 -5 1 4 -7 0 答案等于27,
2 1 -5 8
1 -3 0 9
0 2 -1 -5
1 4 -7 0

答案

r1-2r2,r4-r20 7 -5 -101 -3 0 90 2 -1 -50 7 -7 -9r4-r1,r1-3r30 1 -2 51 -3 0 90 2 -1 -50 0 -2 1r3-2r10 1 -2 51 -3 0 90 0 3 -150 0 -2 1r4+(2/3)r30 1 -2 51 -3 0 90 0 3 -150 0 0 -9交换1,2行后为上三角行列式...