Помогите пожалуйста упростить выражение: номер 5.21. Заблаговременно

1) (a+b) - (a-b) = 2b * 2a = 4ab

2) (m+4) - 4 (m+1) = m + 8m + 16 - 4 (m + 2m +1) = m + 8m + 16 - 4m - 8m - 4 = -3m + 12

3) 3(2-y) + 4(y-5) = 3(4-4y+y) + 4(y - 10y + 25) = 12 - 12y + 3y + 4y - 40y + 100 = 112 - 52y + 7y = 7y - 52y + 112

4) 5(3-5x) - 5(3x-7) * (3x+7) = 5 ((3-5x) - (3x-7) * (3x+7)) = 5 (9-30x + 25x - (9x - 49)) = 5 (9 - 30x + 25x - 9x + 49) = 5 (58 - 30x + 16x) = 5 * 2 (29 - 15x + 8x) = 10 (29 - 15x + 8x)

5) (a+1) + 3(a-1) - 5 (a-1)* (a+1) = a + 2a + 1 + 3 (a - 2a + 1) - 5 (a -1) = a + 2a + 1 + 3a - 6a + 3 - 5a + 5 = -a - 4a + 9

6) (x-1) - 4(x+1) - 6 (x+1) * (x-1) = x  - 2x + 1 - 4 (x + 2x + 1) - 6 (x -1) = x - 2x + 1 - 4x - 8x - 4 - 6x + 6 = -9x - 10x + 3.