5a - 5b - ay + by = (5a - 5b) - (ay - by) = 5(a - b) - y(a - b) = (a - b)(5 - y)
3x + 3y + kx + ky = (3x + 3y) + (kx + ky) = 3(x + y) + k(x + y) = (x + y)(3 + k)
2ax + 6ay + 3by + bx = (2ax + 6ay) + (3by + bx) = 2a(x + 3y) + b(3y + x) =
= (x + 3y)(2a + b)
ty + 12zx + 3tx + 4zy = (ty + 3tx) + (12zx + 4zy) = t(y + 3x) + 4z(3x + y) =
= (3x + y)(t + 4z)