> 数学 >
在数列{an}中,a1=2,an+1=an+ln(1+
1
n
),则an=(  )
A. 2+lnn
B. 2+( n-1 ) lnn
C. 2+nlnn
D. 1+n+lnn
人气:340 ℃ 时间:2020-09-14 13:38:52
解答
∵在数列{an}中,a1=2,an+1=an+ln(1+
1
n
),∴an+1an=ln
n+1
n

∴an=(an-an-1)+(an-1-an-2)+…+(a2-a1)+a1
=ln
n
n−1
+ln
n−1
n−2
+
…+ln
2
1
+2
=ln(
n
n−1
n−1
n−2
•…•
2
1
)+2

=lnn+2.
故选A.
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