Объяснение:

1) (a-2)(a-1) - a(a+1)= a^2 - a - 2a + 2 - a^2 - a= -a -2a + 2 - a= -4a + 2

2) (b-5)(b+10) + (b+6)(b-8)= b^2 + 10b - 5b - 50 + b^2 - 8b - 6b + 48= 2b^2 - 9b - 2

3) (2c + 3)(3c + 2) - (2c +7)(2c - 7)= 6c^2 + 4c + 9c + 6 -(4c^2 - 49)= 6c^2 + 4c + 9c + 6 - 4c^2 + 49= 2c^2 + 13 + 55

4) (3d + 5)(5d - 1) - (6d - 3)(2 - 8d)= 15d^2 - 3d + 25d - 5d -(12d - 48d^2 - 6 + 24d^2)= 15d^2 - 3d + 25d - 5d -(36d - 48d^2 - 6)= 15d^2 - 3d + 25d - 5d - 36d +48d^2 - 6= 63d^2 - 14d +1