问题
选择题
数列{an}满足an+1=
|
答案
∵a1=
| 2 |
| 5 |
| 1 |
| 2 |
∴a2=
| 4 |
| 5 |
| 1 |
| 2 |
∴a3=
| 3 |
| 5 |
a4=
| 1 |
| 5 |
a5=
| 2 |
| 5 |
∴数列具有周期性，且周期为4，
∴a2009=a1=
| 2 |
| 5 |
故选B
搜题请搜索小程序“爱下问搜题”
数列{an}满足an+1=
|
∵a1=
| 2 |
| 5 |
| 1 |
| 2 |
∴a2=
| 4 |
| 5 |
| 1 |
| 2 |
∴a3=
| 3 |
| 5 |
a4=
| 1 |
| 5 |
a5=
| 2 |
| 5 |
∴数列具有周期性，且周期为4，
∴a2009=a1=
| 2 |
| 5 |
故选B