数列{a
n}的前n项和记为S
n,a
1=t,a
n+1=2S
n+1(n∈N
*).
(1)当t为何值时,数列{a
n}为等比数列?
(2)在(1)的条件下,若等差数列{b
n}的前n项和T
n有最大值,且T
3=15,又a
1+b
1,a
2+b
2,a
3+b
3成等比数列,求T
n.
考点分析:
相关试题推荐
如图,在某港口A处获悉,其正东方向20海里B处有一艘渔船遇险等待营救,此时救援船在港口的南偏西30°据港口10海里的C处,救援船接到救援命令立即从C处沿直线前往B处营救渔船.
(Ⅰ) 求接到救援命令时救援船据渔船的距离;
(Ⅱ)试问救援船在C处应朝北偏东多少度的方向沿直线前往B处救援?(已知cos49°=
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101006059724071/SYS201311031010060597240021_ST/0.png)
).
查看答案
已知向量
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101006059724071/SYS201311031010060597240020_ST/0.png)
=(cosωx-sinωx,sinωx),
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101006059724071/SYS201311031010060597240020_ST/1.png)
=(-cosωx-sinωx,2
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101006059724071/SYS201311031010060597240020_ST/2.png)
cosωx),设函数f(x)=
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101006059724071/SYS201311031010060597240020_ST/3.png)
•
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101006059724071/SYS201311031010060597240020_ST/4.png)
+λ(x∈R)的图象关于直线x=π对称,其中ω,λ为常数,且ω∈(
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101006059724071/SYS201311031010060597240020_ST/5.png)
,1)
(1)求函数f(x)的最小正周期;
(2)若y=f(x)的图象经过点(
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101006059724071/SYS201311031010060597240020_ST/6.png)
,0)求函数f(x)在区间[0,
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101006059724071/SYS201311031010060597240020_ST/7.png)
]上的取值范围.
查看答案
已知函数f(x)=sin x+tan x,项数为27的等差数列{a
n}满足a
n∈(-
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101006059724071/SYS201311031010060597240019_ST/0.png)
),且公差d≠0,若f(a
1)+f(a
2)+…f(a
27)=0,则当k=
时,f(a
k)=0.
查看答案
若方程lgkx=2lg(x+1)仅有一个实根,那么k的取值范围是
.
查看答案
若不等式
![manfen5.com 满分网](http://img.manfen5.com/res/GZSX/web/STSource/20131103101006059724071/SYS201311031010060597240017_ST/0.png)
对一切非零实数x恒成立,则实数a的取值范围是
.
查看答案