3x(x-4)-6(x²+2x)= 3х^2-12x-6x^2-12x=-3x^2-24x многочлен 2 степени
2y(x-y)+y(7y-3x)=2yx-2y^2+7y^2-3yx=5y^2-yx
3)
4)10x(5x²-7y)-6x(5y+9x²) = 50x^3-70xy-30xy-54x^3=-4x^3-100xy= 4x^3+100xy
5)7m(m-3n)-15n(3m+n)+4m(-m+8n)=7m^2-21nm-45mn-15^2-4mn+32mn=-8m^2-38mn=8m^2+38mn