Série 2 : exo 4a

[1, 2, 3, 4]
[4, 5, 6, 7]
[6, 7, 8, 9]

L_2 <- L_2 - 4 * L_1

[1,  2,  3,  4]
[0, -3, -6, -9]
[6,  7,  8,  9]

L_3 <- L_3 - 6 * L_1

[1,  2,   3,   4]
[0, -3,  -6,  -9]
[0, -5, -10, -15]

L_2 <- -1/3 * L_2

[1,  2,   3,   4]
[0,  1,   2,   3]
[0, -5, -10, -15]

L_3 <- -1/5 * L_3

[1, 2, 3, 4]
[0, 1, 2, 3]
[0, 1, 2, 3]

L_3 <- L_3 - 1 * L_2

[1, 2, 3, 4]
[0, 1, 2, 3]
[0, 0, 0, 0]

L_1 <- L_1 - 2 * L_2

[1, 0, -1, -2]
[0, 1,  2,  3]
[0, 0,  0,  0]