помогите пож с алгеброй у меня очень плохо с ней !

1) ay - 3y - 4a + 12= (ay - 3y) - (4a - 12)= y(a - 3) - 4(a - 3) = (a - 3)(y - 4)
2) 9a + 9 - na - n = (9a + 9) - (na + n) = 9(a + 1) - n(a + 1) = (a + 1)(9 - n)
3) 6x + ay + 6y + ax = (6x + 6y) + (ay + ax) = 6(x + y) + a(y + x) = (x + y)(6 + a)
4) 8x - 8y + xz - yz = (8x - 8y) + (xz - yz) = 8(x - y) + z(x - y) = (x - y)(8 + z)
5) mn + m - n - 1 = (mn - n) + (m - 1) = n(m - 1) + (m - 1) = (m - 1)(n + 1)
6) ab - ac - 2b + 2c = (ab - ac) - (2b - 2c) = a(b - c) - 2(b - c) = (b - c)(a - 2)