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=1\3,y=-2\3
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(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)/(1/3-2/3)
=(-1/3)/(-1/3)
=1
=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)/(1/3-2/3)
=(-1/3)/(-1/3)
=1
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