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已知1/x+1/y=3,求(-3x+xy-3y)/(3x-2xy+3y)
人气:133 ℃ 时间:2019-12-11 01:04:28
解答
(-3x+xy-3y)/(3x-2xy+3y) =(-3x+2xy-3y)/(3x-2xy+3y)-xy/ (3x-2xy+3y) =-1-1/(3*(1/x+1/y)-2) =-1-1/(9-2) =-1-1/7 =-8/7
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