先化简,再求值;(x^2y-x^3)(x^2+2xy+y^2)÷x(x-y)×(x+y)(x^2-2xy+y^2),已知x=13,y=-23

题目

先化简,再求值;(x^2y-x^3)(x^2+2xy+y^2)÷x(x-y)×(x+y)(x^2-2xy+y^2),已知x=13,y=-23

答案

(x^2y-x^3)/(x^2+2xy+y^2)÷x/(x-y)×(x+y)/(x^2-2xy+y^2)=x^2(y-x)/(x+y)^2÷x/(x-y)×(x+y)/(x-y)^2=x^2(y-x)/(x+y)^2×(x-y)/x×(x+y)/(x-y)^2=x(y-x)/(x+y)×1/(x-y)=-x(x-y)/(x+y)×1/(x-y)=-x/(x+y)=(-1/3)/(1...