2-3r1,r3+r1,r3+r1
3 -1 2 6
0 3 1 -8
0 1 1 -5
0 0 0 4
r2-3r3
3 -1 2 6
0 0 -2 8
0 1 1 -5
0 0 0 4
r2r3 D=(-1)*
3 -1 2 6
0 1 1 -5
0 0 -2 8
0 0 0 4
= -3*1*(-2)*4
= 24.
2-3r1,r3+r1,r3+r1
3 -1 2 6
0 3 1 -8
0 1 1 -5
0 0 0 4
r2-3r3
3 -1 2 6
0 0 -2 8
0 1 1 -5
0 0 0 4
r2r3 D=(-1)*
3 -1 2 6
0 1 1 -5
0 0 -2 8
0 0 0 4
= -3*1*(-2)*4
= 24.