（3x^3y+3xy^3-6x^2y^2)/(x^2y^3-x^3y^2)
=3xy(x^2-2xy+xy)/x^2y^2(y-x)
=3xy(x-y)^2/x^2y^2(y-x)
=3(y-x)/xy
y是多少你第二部中+xy怎么来的（3x^3y+3xy^3-6x^2y^2)/(x^2y^3-x^3y^2)=3xy(x^2-2xy+y^2)/x^2y^2(y-x)=3xy(x-y)^2/x^2y^2(y-x)=3(y-x)/xy写错了最后一部还是有些不明白分子分母的公因式约去