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