已知数列{an}中,a1=1,a2n+1+an2+1=2(an+1an+an+1-an),求数列1a1a2,1a2a3,…,1anan+1,…的前n项

2025-05-18 07:04:37
推荐回答(1个)
回答1:

∵an+12+an2+1=2(an+1an+an+1-an
∴an+12-2an+1?an+an2-2(an+1-an)+1=0
∴(an+1-an2-2(an+1-an)+1=0
∴(an+1-an-1)2=0
∴an+1-an=1∴{an}为等差数列
∴an=a1+(n-1)?1=n
∴Sn=

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
=
n
n+1