1. (a+6) (a-3) + (a-4) (a+5)

2. (y-8) (2y-1) - (3y+1) (5y-2)

3. (3m-4n) (3m+5n) - (4,5m-n) (2m+4n)

4. (x^2 - 2y) (x^3 + 7y) - 6x^3 (x^2 - 8y)

1. (a+6) (a-3) + (a-4) (a+5) = а²+3 а-18+а²+а-20=2 а²+4 а-22. (y-8) (2y-1) - (3y+1) (5y-2) = 2 у²-17 у+8-15 у²+у+2=-13 у²-16 у+10

3. (3m-4n) (3m+5n) - (4,5m-n) (2m+4n) =

= 9m² + 3mn - 20n² - 9m² - 16mn + 4n² = - 16mn-16n²

4. (x^2 - 2y) (x^3 + 7y) - 6x^3 (x^2 - 8y) = x^5+7x²y-2x³y-14y³-6x^5+48x³y=

=-5x^5+46x³y+7x²y-14y³