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已知数列{an}满足a1=2,an+1
1+an
1−an
(n∈N*)
,则a1a2a3…a2010的值为(  )
A. 1
B. -3
C. 2
D. -6
人气:205 ℃ 时间:2019-09-22 06:31:22
解答
1=2,an+1
1+an
1−an
(n∈N*)

a2
1+a1
1−a1
=
1+2
1−2
=-3,
a3
1+a2
1−a2
=
1−3
1+3
=−
1
2

a4
1+a3
1−a3
=
1−
1
2
1+
1
2
=
1
3

a5
1+a4
1−a4
=
1+
1
3
1−
1
3
=2=a1
∴a6=a2,a7=a3,…,a2009=a1,a2010=a2
数列{an}是以4为周期的周期数列,且a1a2a3a4=2×(−3)×(−
1
2
1
3
=1

∴a1a2a3…a2010=-6
故选D
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