已知1/x-1/y=3,求3x-5xy-3y/x-2xy-y的值.要过程阿已知1/x-1/y=3,求3x-5xy-3y/x-2xy-y的值.要讲解阿

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已知1/x-1/y=3,求3x-5xy-3y/x-2xy-y的值.要过程阿已知1/x-1/y=3,求3x-5xy-3y/x-2xy-y的值.要讲解阿
已知1/x-1/y=3,求3x-5xy-3y/x-2xy-y的值.要过程阿
已知1/x-1/y=3,求3x-5xy-3y/x-2xy-y的值.要讲解阿

已知1/x-1/y=3,求3x-5xy-3y/x-2xy-y的值.要过程阿已知1/x-1/y=3,求3x-5xy-3y/x-2xy-y的值.要讲解阿
1/x-1/y=3
通分有y-x/xy=3 所以y-x=3xy
(3x-5xy-3y)/(x-2xy-y)=[3(x-y)-5xy]/[(x-y)-2xy]=(-9xy-5xy)/(-3xy-2xy)
=(-14xy)/(-5xy)=14/5

由1/x-1/y=3可知，x,y≠0
(3x-5xy-3y)/(x-2xy-y)上下同除以xy
得到
(3/y-5-3/x)/(1/y-2-1/x)
=[3(1/y-1/x)-5]/[(1/y-1/x)-2]
=(-9-5)/(-3-2)
=14/5

1/x－1/y＝3
y－x＝3xy
﹙3x－5xy－3y﹚/﹙x－2xy－y﹚
＝[3﹙x－y﹚－5xy]/[﹙x－y﹚－2xy]
＝﹙﹣9xy－5xy﹚/﹙﹣3xy－2xy﹚
＝﹙﹣14xy﹚/﹙﹣5xy﹚
＝14/5.

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