15 x y - 25y^2 = 5y (3x - 5y)
12a^5 - 4a^4 = 4a^4 (3a - 1)
6a-6y+ab-by = 6(a-y) + b(a-y) = (6+b)(a-y)
15 x y - 25y^2 = 5y (3x - 5y)
12a^5 - 4a^4 = 4a^4 (3a - 1)
6a-6y+ab-by = 6(a-y) + b(a-y) = (6+b)(a-y)