1MS : 2.5.21 s

[ 1,  2,  3,   9]
[ 1, -1,  4,  15]
[-1,  7, -6, -27]

L_2 <- L_2 - 1 * L_1

[ 1,  2,  3,   9]
[ 0, -3,  1,   6]
[-1,  7, -6, -27]

L_3 <- L_3 + 1 * L_1

[1,  2,  3,   9]
[0, -3,  1,   6]
[0,  9, -3, -18]

L_3 <- L_3 + 3 * L_2

[1,  2, 3, 9]
[0, -3, 1, 6]
[0,  0, 0, 0]

L_2 <- -1/3 * L_2

[1, 2,    3,  9]
[0, 1, -1/3, -2]
[0, 0,    0,  0]