正项数列{an}满足,a1=1,a2n+1=a2n+2an+1,则1a1a2+1a2a3+…1anan+1=(  )A.2?2nB.1?1nC.1?1n+1

2025-05-18 10:15:05
推荐回答(1个)
回答1:

an+12an2+2an+1=(an+1)2且an>0
∴an+1=an+1
∵a1=1
∴数列{an}是以1为首项,以1为公差的等差数列
∴an=1+n-1=n

1
an+1an
=
1
n(n+1)
=
1
n
?
1
n+1

1
a1a2
+
1
a2a3
+…+
1
anan+1

=
1
1×2
+
1
2×3
+…+
1
n(n+1)

=1-
1
2
+
1
2
?
1
3
+…+
1
n
?
1
n+1

=1-
1
n+1

故选C