r2+5r1,r3-2r1,r4-3r1
1 -5 3 -3
0 -24 18 -19
0 10 -5 5
0 16 -10 11
第3行提出5, D=5*
1 -5 3 -3
0 -24 18 -19
0 2 -1 1
0 16 -10 11
r2+12r3,r4-8r3
1 -5 3 -3
0 0 6 -7
0 2 -1 1
0 0 -2 3
r2+3r4
1 -5 3 -3
0 0 0 2
0 2 -1 1
0 0 -2 3
r2<->r3,r3<->r4
1 -5 3 -3
0 2 -1 1
0 0 -2 3
0 0 0 2
D = 5*2*(-2)*2 = -40.