![](https://static.youtibao.com/asksite/comm/h5/images/m_q_title.png)
[单选题]
设数列{an}为等差数列,公差d=-2,Sn为其前n项和,若S10=S11,则a1=()
A.18
B.20
C.22
D.24
![](https://static.youtibao.com/asksite/comm/h5/images/m_q_a.png)
B、20
![](https://static.youtibao.com/asksite/comm/h5/images/solist_ts.png)
A.18
B.20
C.22
D.24
B、20
A.(1)(2)
B.(1)(3)
C.(2)(3)
D.(1)(2)(3)
A.等比数列32,16,8,4的公比是2
B.等差数列-1,-2,-3,-4的公差是-1
C.常数列a,a,a,a,……既是等差数列,又是等比数列
D.以上选项都正确
已知一个等差数列的首项为1,公差为3,那么该数列的前5项和为 ()
A.35
B.30
C.20
D.10
等差数列{an}的公差d<0,且a2·a4=12,a2+a4=8,则数列{an}的通项公式是()
A.an=2n-2
B.an=2n+4
C.an=-2n+12
D.an=-2n+10
等差数列{an}的公差d<0,且n2·n4=12,a2+a4=8,则数列{an}的通项公式是
A.an=2n-2(n∈N*)
B.an=2n+4(n∈N*)
C.an=-2n+12(n∈N*)
D.an=-2n+10(n∈N*)