(x-y)/xy=3
1/y-1/x=3
（2x+3xy-2y）/（x-2xy-y）
=(2/y+3-2/x)/(1/y-2-1/x)…………这一步分子分母同除以xy
=[3+2(1/y-1/x)]/[-2+(1/y-1/x)]
=(3+2×3)/(-2+3)
=9
∵x-y/xy=3
∴x-y=3xy
2x+3xy-2y/x-2xy-y
=[2(x-y)+3xy]/[(x-y)-2xy]
=(6xy+3xy)/(3xy-2xy)
=9xy/(xy)
=9
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