Ax + ay + 2x + 2y = (ax + 2x) + (ay + 2y) = x(a + 2) + y(a + 2) = (x + y)(a + 2)
3b + 3b² - a - ab = (3b + 3b²) - (a + ab) = 3b(1 + b) - a(1 + b) = (3b - a)(1 + b)
18a² - 27ab + 14ac - 21bc = (18a² - 27 ab) + (14ac - 21bc) = 9a(2a - 3b) + 7c(2a - 3b) = (9a + 7c)(2a - 3b)