题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042727-14636.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042728-90641.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042728-67745.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042728-67933.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042728-90641.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042728-67745.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042728-67933.png)
| 第一列 | 第二列 | 第三列 |
第一行 | 3 | 2 | 10 |
第二行 | 6 | 4 | 14 |
第三行 | 9 | 8 | 18 |
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042727-14636.png)
(Ⅱ)若数列
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042728-35652.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042729-43488.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042728-35652.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042729-16147.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042729-83389.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042729-92724.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042729-29758.png)
解析
试题分析:(I)当
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042730-13068.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042730-64787.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042730-99266.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042730-50086.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042731-59890.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042729-92724.png)
(II)因为
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042731-60888.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042731-69167.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042731-28934.png)
当n为偶数时,
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042731-19767.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042732-18107.png)
当n为奇数时,
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042732-12496.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042732-63721.png)
综上所述,
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042732-77056.png)
点评:本题考查的是数列求和问题.在解答的过程当中充分体现了分类讨论的思想、分组求和的方法、等比数列通项的求法以及运算能力.值得同学们体会和反思.
核心考点
试题【等比数列中,,,分别是下表第一、二、三行中的某一个数,且,,中的任何两个数不在下表的同一列. 第一列第二列第三列第一行3210第二行6414第三行9818(Ⅰ)】;主要考察你对数列综合等知识点的理解。[详细]
举一反三
已知
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042717-59725.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042717-62229.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042717-58613.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042717-12183.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042717-87980.png)
(Ⅰ)求
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042717-59725.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042717-62229.png)
(Ⅱ)若
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042718-85480.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042718-78705.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042718-37528.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042718-42991.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042711-96124.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042711-54666.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042701-63245.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042701-56127.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042701-91133.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042702-60472.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042702-89746.png)
(Ⅰ)求数列{
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042701-63245.png)
(Ⅱ)若数列{
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042702-90297.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042702-43833.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042702-63990.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042651-19839.png)
A.若![]() ![]() ![]() |
B.若![]() ![]() ![]() |
C.若![]() ![]() ![]() |
D.若![]() ![]() ![]() |
已知数列{ an}的前n项和为Sn,且Sn=2an-l;数列{bn}满足bn-1=bn=bnbn-1(n≥2,n∈N*)b1=1.
(Ⅰ)求数列{an},{bn}的通项公式;
(Ⅱ)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015042639-93307.png)
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