1.由a1=1,d=3确定的等差数列{an},当an=298时,序号n等于( )
A.99 B.100 C.96 D.101
2.(2018湖南长郡中学仿真,6)已知等差数列{an}满足an+1+an=4n,则a1=( )
A.-1 B.1 C.2 D.3
3.(2018河南商丘二模,3)已知等差数列{an}的公差为d,且a8+a9+a10=24,则a1·d的最大值为( )
A. B. C.2 D.4
4.在等差数列{an}中,a3+a6=11,a5+a8=39,则公差d为 ( )
A.-14 B.-7 C.7 D.14
5.已知等差数列{an}的前n项和为Sn,且3a3=a6+4,若S5<10,则a2的取值范围是( )
A.(-∞,2) B.(-∞,0)
C.(1,+∞) D.(0,2)
6.已知Sn是等差数列{an}的前n项和,则2(a1+a3+a5)+3(a8+a10)=36,则S11=( )
A.66 B.55 C.44 D.33
7.(2018湖南衡阳一模,15)已知数列{an}前n项和为Sn,若Sn=2an-2n,则Sn= .
8.设数列{an}{bn}都是等差数列,若a1+b1=7,a3+b3=21,则a5+b5= .
