已知x加y分之xy等于2,求负x加3xy减y分之3x减5xy加3y

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已知x加y分之xy等于2,求负x加3xy减y分之3x减5xy加3y

已知 xy/(x+y) = 2,求:(3x-5xy+3y)/(-x+3xy-y)
xy/(x+y) = 2得:xy=2(x+y)
(3x-5xy+3y)/(-x+3xy-y)
=(3x-9xy+3y+4xy)/(-x+3xy-y)
= -3 + 4xy/(-x+3xy-y)
= -3 + 8(x+y)/(-x+6x+6y-y)
= -3 + 8(x+y)/5(x+y)
= -3 + 8/5
= -7/5

将x+y换掉。最后xy都约了。就是这个答案