3-r1
1 2 3 4 -4
0 1 -1 1 2
0 1 -3 -1 3
0 -2 1 1 2
r1+r4,r3-r2,r4+2r2
1 0 4 5 -2
0 1 -1 1 2
0 0 -2 -2 1
0 0 -1 3 6
r1+2r3,r4*(-1),r2+r4,r3+2r4
1 0 0 1 0
0 1 0 -2 -4
0 0 0 -8 -11
0 0 1 -3 -6
r3*(-11/8),r1-r3,r2+2r3,r4+4r3
1 0 0 0 -11/8
0 1 0 0 -10/8
0 0 0 1 11/8
0 0 1 0 -15/8
r3r4
1 0 0 0 -11/8
0 1 0 0 -10/8
0 0 1 0 -15/8
0 0 0 1 11/8