满分5 >
高中数学试题 >
等差数列{an}的前n项和为Sn,若a3+a17=10,则S19=( ) A.1...
等差数列{an}的前n项和为Sn,若a3+a17=10,则S19=( )
A.190
B.95
C.170
D.85
考点分析:
相关试题推荐
等差数列{a
n}的前四项之和为40,最后四项之和为80,所有项之和是210,则项数n为( )
A.12
B.14
C.15
D.16
查看答案
等比数列{a
n}的首项a
1=1,公比为q,前n项和是S
n,则数列
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101729076938828/SYS201311031017290769388004_ST/0.png)
的前n项和是( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101729076938828/SYS201311031017290769388004_ST/1.png)
B.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101729076938828/SYS201311031017290769388004_ST/2.png)
C.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101729076938828/SYS201311031017290769388004_ST/3.png)
D.
查看答案
在下列通项公式中,一定不是数列2,4,8,…的通项公式的是( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101729076938828/SYS201311031017290769388003_ST/0.png)
B.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101729076938828/SYS201311031017290769388003_ST/1.png)
C.a
n=2n
D.
查看答案
在△ABC中,A=60°,b=16,面积
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101729076938828/SYS201311031017290769388002_ST/0.png)
,则a等于( )
A.
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101729076938828/SYS201311031017290769388002_ST/1.png)
B.75
C.49
D.51
查看答案
在△ABC中,a
2=b
2+c
2+bc,则A等于( )
A.120°
B.60°
C.45°
D.30°
查看答案