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问题 选择题

已知定义在R上的函数f(x)是偶函数,对x∈R都有f(2+x)=f(2-x),当f(-3)=-2时,f(2007)的值为(　　)

A．2

B．-2

C．4

D．-4

答案

答案：B

∵函数f(x)是R上的偶函数,

∴f(2+x)=f(2-x)=f(x-2),

∴f(x+4)=f(x),

故函数f(x)是以4为周期的偶函数,

∴f(2007)=f(3)=f(-3)=-2.

单项选择题

Both bus and tree topologies are characterized by the use of multipoint（）．For the bus，all stations attach，through appropriate hardware（）known as a tap，directly to a linear transmission medium，or bus．Full-duplex operation between the station and the tap allows data to be transmitted onto the bus and received from the（）．A transmission from any station propagates the length of the medium in both directions and can be received by all other（）．At each end of the bus is a（），which absorbs any signal，removing it from the bus．

Full-duplex operation between the station and the tap allows data to be transmitted onto the bus and received from the（）．

A．tree

B．bus

C．star

D．ring
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单项选择题

符号表示的是（）。

A.波音

B.回音

C.颤音

D.滑音
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