Série 2 : exo 4b

[1, 3, 5, 7]
[3, 5, 7, 9]
[5, 7, 9, 1]

L_2 <- L_2 - 3 * L_1

[1,  3,  5,   7]
[0, -4, -8, -12]
[5,  7,  9,   1]

L_3 <- L_3 - 5 * L_1

[1,  3,   5,   7]
[0, -4,  -8, -12]
[0, -8, -16, -34]

L_2 <- -1/4 * L_2

[1,  3,   5,   7]
[0,  1,   2,   3]
[0, -8, -16, -34]

L_3 <- -1/8 * L_3

[1, 3, 5,    7]
[0, 1, 2,    3]
[0, 1, 2, 17/4]

L_3 <- L_3 - 1 * L_2

[1, 3, 5,   7]
[0, 1, 2,   3]
[0, 0, 0, 5/4]

L_1 <- L_1 - 3 * L_2

[1, 0, -1,  -2]
[0, 1,  2,   3]
[0, 0,  0, 5/4]

L_3 <- 4/5 * L_3

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