(2014•北京模拟)若Sn是等差数列{an}的前n项和,且S8-S3=20,则S11的值为______.
1个回答
∵S
8
-S
3
=a
4
+a
5
+a
6
+a
7
+a
8
=20
由等差数列的性质可得,5a
6
=20
∴a
6
=4
由等差数列的求和公式可得s
11
=
11(a1+a11)
2=11a
6
=44
故答案为:44.
相关问题
若Sn是等差数列{an}的前n项和,且S8-S3=10,则S11的值为______.
若Sn是等差数列{an}的前n项和,且S8-S4=12,则S12的值为( )
(2014•北京模拟)已知等差数列{an}的前n项和为Sn,若a2=1,S5=10,则S7=______.
等差数列{an}中,Sn是前n项和,且S3=S8,S7=Sk,则k的值为( )
设等差数列an前n项和为sn,且s10=s20.则s30=?
等差数列an中,前n项和为Sn,且S6S8,则:
已知{an}为等差数列,Sn为{an}的前n项和,n∈N*,若a3=16,S20=20,则S10值为______.
已知{an}为等差数列,Sn为{an}的前n项和,n∈N*,若a3=16,S20=20,则S10值为______.
等差数列前n项和的问题等差数列{an}的前n项和为sn,若s3=3,s6=9,则s9=?
设等差数列{an}的前n项和Sn,且S4/S8=1/3,则S8/S16=?