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> 已知1x-1y=2,则5x+xy-5yx-xy-y等于()A.13B.-13C.-3D.3-数学
已知1x-1y=2,则5x+xy-5yx-xy-y等于()A.13B.-13C.-3D.3-数学
题目简介
已知1x-1y=2,则5x+xy-5yx-xy-y等于()A.13B.-13C.-3D.3-数学
题目详情
已知
1
x
-
1
y
=2
,则
5x+xy-5y
x-xy-y
等于( )
A.
1
3
B.-
1
3
C.-3
D.3
题型:单选题
难度:中档
来源:不详
答案
∵
class="stub"1
x
-
class="stub"1
y
=
class="stub"y-x
xy
=2,即y-x=2xy,
∴x-y=-2xy,
则
class="stub"5x+xy-5y
x-xy-y
=
5(x-y)+xy
(x-y)-xy
=
class="stub"-10xy+xy
-2xy-xy
=
class="stub"-9xy
-3xy
=3.
故选D
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计算(1)12xy5a÷9x2y(2)先化简,再求
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题目简介
已知1x-1y=2,则5x+xy-5yx-xy-y等于()A.13B.-13C.-3D.3-数学
题目详情
答案
∴x-y=-2xy,
则
故选D