Factories:
6ab – b2 + 12ac – 2bc
= 6ab + 12ac – b2 – 2bc
= (6ab + 12ac) – (b2 + 2bc)
= 6a(b + 2c) – b(b + 2c)
= (b + 2c)(6a – b)
So we get,
6ab – b2 + 12ac – 2bc = (b + 2c)(6a – b)