已知1x+1y=3,则3x+xy+3yx-xy+y的值等于()A.5B.10C.15D.20-数学

题目简介

已知1x+1y=3,则3x+xy+3yx-xy+y的值等于()A.5B.10C.15D.20-数学

题目详情

已知
1
x
+
1
y
=3,则
3x+xy+3y
x-xy+y
的值等于(  )
A.5B.10C.15D.20
题型:单选题难度:偏易来源:不详

答案

class="stub"1
x
+class="stub"1
y
=3

∴通分得x+y=3xy,
class="stub"3x+xy+3y
x-xy+y
=
3(x+y)+xy
(x+y)-xy
=class="stub"9xy+xy
3xy-xy
=class="stub"10xy
2xy
=5

故选A.

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