Ay - 12bx + 3ax - 4by = (ay - 4by) - (12bx - 3ax) = y(a - 4b) - 3x(4b - a) =
= y (a - 4b) + 3x(a - 4b) = (a - 4b)(y + 3x)
3c + 3c² - a - ac = (3c - a) + (3c² - ac) = (3c - a) + c(3c - a) = (3c - a)(1 + c)
a²b² + ab + abc + c = (a²b² + ab) + ( abc + c) = ab(ab + 1) + c(ab + 1) =
= (ab + 1)(ab + c)