满分5 >
高中数学试题 >
等差数列an的前n项和为Sn,若a3+a9+a15+a17=0,则S21的值是(...
等差数列an的前n项和为Sn,若a3+a9+a15+a17=0,则S21的值是( )
A.1
B.-1
C.0
D.不能确定
考点分析:
相关试题推荐
不等式(a-2)x
2+2(a-2)x-4<0对x∈R恒成立,则实数a的取值范围是( )
A.(-∞,2)
B.[-2,2]
C.(-2,2]
D.(-∞,-2)
查看答案
设{a
n}是有正数组成的等比数列,S
n为其前n项和.已知a
2a
4=1,S
3=7,则S
5=( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101703368856097/SYS201311031017033688560014_ST/0.png)
B.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101703368856097/SYS201311031017033688560014_ST/1.png)
C.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101703368856097/SYS201311031017033688560014_ST/2.png)
D.
查看答案
如图,椭圆
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101703368856097/SYS201311031017033688560013_ST/0.png)
上的点M到焦点F
1的距离为2,N为MF
1的中点,则|ON|(O为坐标原点)的值为( )
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101703368856097/SYS201311031017033688560013_ST/images1.png)
A.4
B.2
C.8
D.
查看答案
不等式(x-2y+1)(x+y-3)≤0表示的平面区域是( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101703368856097/SYS201311031017033688560012_ST/images0.png)
B.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101703368856097/SYS201311031017033688560012_ST/images1.png)
C.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101703368856097/SYS201311031017033688560012_ST/images2.png)
D.
查看答案
下列有关命题的说法中错误的是( )
A.若p∧q为假命题,则p、q均为假命题
B.“x=1”是“x
2-3x+2=0”的充分不必要条件
C.命题“若x
2-3+2=0,则x=1“的逆否命题为:“若x≠1,则x
2-3x+2≠0”
D.对于命题p:∃x∈R,使得x
2+x+1<0,则¬p:∀x∈R,均有x
2+x+1≥0
查看答案