1MS : 2.5.21 q

[2, -1,  3,  4]
[3,  4, -1, -5]
[1,  5, -4, -9]

L_1 <-> L_3

[1,  5, -4, -9]
[3,  4, -1, -5]
[2, -1,  3,  4]

L_2 <- L_2 - 3 * L_1

[1,   5, -4, -9]
[0, -11, 11, 22]
[2,  -1,  3,  4]

L_3 <- L_3 - 2 * L_1

[1,   5, -4, -9]
[0, -11, 11, 22]
[0, -11, 11, 22]

L_3 <- L_3 - 1 * L_2

[1,   5, -4, -9]
[0, -11, 11, 22]
[0,   0,  0,  0]

L_2 <- -1/11 * L_2

[1, 5, -4, -9]
[0, 1, -1, -2]
[0, 0,  0,  0]