Запишите в виде многочлена: 1) (-7m²-8n²) (-m²+3n²); 2) (8x²-3xy) (3x³-xy); 3) (7х³y²-²y²+5xy³).

(-7m²-8n²) (-m²+3n²)=7m^4-21m^2n^2+8m^2n^2-24n^4=7m^4-13m^2n^2-24n^4
 (8x²-3xy) (3x³-xy)=8 x^5+8x^3y-9x^6y+3x^2y^2

(7х³y²-xy)(-2x²y²+5xy³).=-14x^5y^4+35x^4y^5+2x^3y^3-5x^2y^4