问题 选择题
f(x)满足对任意的实数a,b都有f(a+b)=f(a)•f(b),且f(1)=2,则
f(2)
f(1)
+
f(4)
f(3)
+
f(6)
f(5)
+…+
f(2010)
f(2009)
=(  )
A.1003B.2010C.2008D.1004
答案

由题意,取a=n(n为正整数),b=1,可得

f(n+1)=f(n)f(1),即

f(n+1)
f(n)
=f(1)=2

f(2)
f(1)
=
f(4)
f(3)
=
f(6)
f(5)
=…=
f(2010)
f(2009)
=2共1005项,

f(2)
f(1)
+
f(4)
f(3)
+
f(6)
f(5)
+…+
f(2010)
f(2009)
=1005×2=2010

故选B

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