(x一y)(x^2+xy+y^2）=x(x^2+xy+y^2)-y(x^2+xy+y^2)=x^3+x^2y+xy^2-yx^2-xy^2-y^3=x^3-y^3那(ab^2)^3÷(ab)^2呢(ab^2)^3÷(ab)^2=a^3*b^6/a^2*b^2=a^(3-2)*b^(6-2)=ab^4