题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124417-52035.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124417-50552.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124417-50552.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124417-25039.png)
(1)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124417-52035.png)
(2) 令
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124417-67379.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124418-68400.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124418-54514.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124418-54514.png)
(3)若数列
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124418-30645.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124418-76396.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124418-44567.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124419-60547.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124419-43784.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124419-65152.png)
(2)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124419-99275.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124420-66796.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124420-29173.png)
(3)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124420-52439.png)
解析
(1)利用数列
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124417-52035.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124417-50552.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124417-50552.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124417-25039.png)
(2)利用裂项求和的思想,找到通项公式的特点,再累加得到
(3)假设存在这样的实数,满足条件,
然后根据假设得到
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124420-82259.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124420-52439.png)
(1)n=1时,
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124421-57750.png)
n
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124421-14432.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124421-86648.png)
(2)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124421-30482.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124422-24436.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124420-66796.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124420-29173.png)
(3)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124422-49489.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124422-56418.png)
假设存在这样的实数,满足条件,
又
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124422-44392.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124423-94247.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124423-23925.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124423-78642.png)
即:
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124423-54203.png)
解得:
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124420-52439.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124424-75820.png)
数列
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124424-92814.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124420-52439.png)
核心考点
试题【 已知数列的前n项和为,且,(1)求数列的通项公式;(2) 令,且数列的前n项和为,求;(3)若数列满足条件:,又,是否存在实数,使得数列为等差数列?】;主要考察你对等差数列等知识点的理解。[详细]
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124111-35924.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124111-57435.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124112-75981.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124112-39162.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124112-89376.png)
(I)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124111-35924.png)
(II)设数列
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010124112-11532.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010123611-51603.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010123611-33054.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010123611-74068.png)
A.56 | B.58 | C.62 | D.60 |
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010123557-20478.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010123558-56613.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010123558-40742.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010123558-32165.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010123558-71184.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010123401-44013.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010123401-60408.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010123402-31632.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010123402-95492.png)
A.30 | B.27 | C.24 | D.21 |
已知数列
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010121715-64547.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010121716-63608.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010121716-98559.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010121716-69613.png)
(1) 求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010121715-64547.png)
(2) 设区间
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010121716-73368.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010121716-34081.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010121717-56298.png)
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