2. Упростите выражение: 1) (x−2)(x−11)−2x(4−3x); 2) (a+6)(a−3)+(a−4)(a+5); 3) (y−8)(2y−1)−(3y+1)(5y−2); 4) (3m−4n)(3m+5n)−(4,5m−n)(2m+4n); 5) (x^2+2y)(x^3+7y)−6x^3(x^2−8y).

1. \((x-2)(x-11)-2x(4-3x)=x^2-13x+22-8x+6x^2=7x^2-21x+22\).
2. \((a+6)(a-3)+(a-4)(a+5)=a^2+3a-18+a^2+a-20=2a^2+4a-38\).
3. \((y-8)(2y-1)-(3y+1)(5y-2)=2y^2-17y+8-(15y^2-y-2)=-13y^2-16y+10\).
4. \((3m-4n)(3m+5n)=9m^2+3mn-20n^2\); \((4.5m-n)(2m+4n)=9m^2+16mn-4n^2\). Поэтому \(9m^2+3mn-20n^2-(9m^2+16mn-4n^2)=-13mn-16n^2\).
5. \((x^2+2y)(x^3+7y)=x^5+7x^2y+2x^3y+14y^2\), а \(6x^3(x^2-8y)=6x^5-48x^3y\). Следовательно, \(x^5+7x^2y+2x^3y+14y^2-6x^5+48x^3y=-5x^5+50x^3y+7x^2y+14y^2\).

Ответ: 1) \(7x^2-21x+22\); 2) \(2a^2+4a-38\); 3) \(-13y^2-16y+10\); 4) \(-13mn-16n^2\); 5) \(-5x^5+50x^3y+7x^2y+14y^2\).