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幼苗
共回答了16个问题采纳率:100% 举报
(1)2x-3/(x-1)(x-4) - x-2/(1-x)(4-x)
=(2x-3)/(x-1)(x-4) - (x-2)/(x-1)(x-4)
=(2x-3-x+2)/(x-1)(x-4)
=(x-1)/(x-1)(x-4)
=1/(x-4)
(x^2-y^2)/xy - (xy-y^2)/x(y-x)
=(x^2-y^2)/xy +y(x-y)/x(x-y)
= (x^2-y^2)/xy +y/x
=(x^2-y^2+y^2)/xy
=x^2/xy
=x/y
(1)2x/x^2y^2 + x/(y^2-x^2) + y/(x-y)(x+y)
=2x/x^2y^2 - x/(x-y)(x+y) + y/(x-y)(x+y)
=2x/x^2y^2 -( x-y)/(x-y)(x+y)
=2/xy^2-1/(x+y)
x=4 y=-3
原式=2/xy^2-1/(x+y)=2/4*9-1/(4-3)=-17/18
1年前
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