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先化简,再求值:(xy-x)/x^2-2xy+y^2*x^2-y^2/x^2,其中:x=-2,y=1/2
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先化简,再求值:(xy-x)/x^2-2xy+y^2*x^2-y^2/x^2,其中:x=-2,y=1/2
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答案和解析
(xy-x)/(x^2-2xy+y^2)*(x^2-y^2)/x^2
=x(y-x)/(x-y)^2*(x+y)(x-y)/x^2
=-(x+y)/x
=-(-2+1/2)/(-2)
=-3/4
=x(y-x)/(x-y)^2*(x+y)(x-y)/x^2
=-(x+y)/x
=-(-2+1/2)/(-2)
=-3/4
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