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问题 解答题

已知函数y=y1-y2，y1与x成反比例，y2与x-2成正比例，且当x=1时，y=-1；当x=3时，y=5，求y与x的函数关系式，并求当x=5时y的值．

答案

设y1=

k1
x
，y2=k2（x-2），则

y=

k1
x
-k2(x-2)

根据题意，得

k1+k2=-1
k1
3
-k2=5

解得：k1=3，k2=-4

∴y=

3
x
+4x-8

当x=5时，y=

3
5
+20-8=12
3
5
．

选择题

             is the capital city of Canada.[ ]

A. Ottawa                 

B. Canberra          

C. London 
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单项选择题

Life insurance, before available only to young, healthy persons, can now be obtained for quite a large proportion of the elderly population, and, sorry, even for pet animals.

A．before young, healthy persons available only,

B．available only to young, healthy persons before,

C．available only to persons young, but more healthy,

D．before young and healthy persons only available to,
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