2+2r1,r4-r1
1 0 -1 2
0 1 1 5
0 1 0 -1
0 3 5 -4
r3-r2,r4-3r2
1 0 -1 2
0 1 1 -3
0 0 -1 -6
0 0 2 -19
r4+2r3
1 0 -1 2
0 1 1 -3
0 0 -1 -6
0 0 0 -31
行列式 = 31.
2+2r1,r4-r1
1 0 -1 2
0 1 1 5
0 1 0 -1
0 3 5 -4
r3-r2,r4-3r2
1 0 -1 2
0 1 1 -3
0 0 -1 -6
0 0 2 -19
r4+2r3
1 0 -1 2
0 1 1 -3
0 0 -1 -6
0 0 0 -31
行列式 = 31.