.
(3Ay + B)*(y - C) = = .
Since it is identical to , we have
3A = 6 and hence A = 2; (1)
B - 3AC = -1, or B - 6C = -1; (2)
BC = 51. (3)
Thus you actually have these two equations to determine B and C:
B - 6C = -1 (2)
BC = 51. (3)
From (2), express B = 6C -1 and substitute it into (3). You will get
(6C-1)*C = 51.
= 0,
Factor left side
(C-3)*(2C+17) = 0.
Since you need C to be positive number (as the condition requires), you have only one possibility: C = 3.
Then B = 6C-1 = 6*3-1 = 17,
and now you have everything to calculate = = = 19.