Помогите! С 7 по 9 номер.

7a) 2y - 18 = 2(y - 9) = 2(y - 3)(y + 3)

7б) 3x + 12x + 12 = 3(x + 4x + 4) = 3(x + 2)

8) x(x - 2)(x + 1) = x(x - 1)

x(x + x - 2x - 2) = x(x - 1)

x(x - x - 2) = x - x

x - x - 2x - x + x = 0

- 2x = 0

x = 0

9a) ax + bx + 6a + 6b = (ax + bx) + (6a + 6b) = x(a + b) + 6(a + b) =

= (a + b)(x + 6)

9б) ab - 2a - 2b + 4 = (ab - 2a) - (2b - 4) = a(b - 2) - 2(b - 2) =

= (b - 2)(a - 2)