m=x^-3xy^+2xy^+3y三次方,n=x三次方-2x^+xy^-5y三次方,则2x-7x^y三次方+5xy^+14y三次方等于多少?

m=x^2-3xy^2+2xy^2+3y^3,n=x^3-2x^2+xy^2-5y^3,则2x-7x^2*y^3+5xy^+14y^3等于多少?3m=3x^2-9xy^2+6xy^2+9y^3n=x^3-2x^2+xy^2-5y^32x-7x^2*y^3+5xy^2+14y^3 =3m-n =3x^2-9xy^2+6xy^2+9y^3-x^3+2x^2-xy^2+5y^3=2x-7x^2...