[1, -11, 0, 3, -12]
[2, -1, 0, 1, 0]
[-3, 2, 2, 1, -9]
[-4, -1, 2, 0, -13]
2*I - II, 3*I + III, 4*I + IV
[0, -21, 0, 5, -24]
[0, -31, 2, 10, -45]
[0, -45, 2, 12, -61]
2*I - II, 12*I - 5*III
[0, -11, -2, 0, -3]
[0, -27, -10, 0, 17]
5*I - II
[0, -28, 0, 0, -32]
-28b = -32
b = 32/28 = 8/7
-11b - 2c = -3
c = (3 - 11*8/7)/2 = -67/14
-21b + 5d = -24
d = 3·(7·8/7 - 8)/5 = 0
2a - b + d = 0
a = (8/7 - 0)/2 = 4/7