题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072258-58259.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072258-88887.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072259-44942.png)
(Ⅰ)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072258-58259.png)
(Ⅱ)数列{
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072259-22359.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072259-98210.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072259-80383.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072259-80383.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072300-22029.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072300-87101.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072300-39320.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072300-99281.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072300-96609.png)
(2)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072301-66495.png)
解析
试题分析:(Ⅰ)设数列
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072301-34995.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072301-86536.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072301-76264.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072302-50226.png)
解得
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072302-12365.png)
由数列
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072258-58259.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072302-50996.png)
数列
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072302-21363.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072300-39320.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072300-99281.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072300-96609.png)
(Ⅱ)记
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072302-24059.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072303-90330.png)
若
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072303-61454.png)
若
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072303-92911.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072303-26183.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072304-42894.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072304-59528.png)
此时
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072304-54079.png)
又
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072259-80383.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072300-22029.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072301-66495.png)
点评:主要是考查了等差数列和等比数列的运用,属于中档题。
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072246-13879.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072246-13879.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072247-89130.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072246-13879.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072247-87885.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072247-89130.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072247-10966.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072247-10966.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072241-41931.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072241-64018.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072241-56852.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072241-22147.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072242-65458.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072241-56852.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072242-12287.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072242-92952.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072241-41931.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072228-68088.png)
①
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072228-83699.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072228-62821.png)
②若
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072228-68088.png)
③若
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072229-12923.png)
④若
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072229-30981.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072229-84318.png)
⑤若
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072229-53362.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072215-18711.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072215-17035.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072215-63307.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072215-40134.png)
A.有最小值![]() | B.有最大值![]() |
C.有最小值![]() | D.有最大值![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072208-50535.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072209-87349.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072209-26588.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072209-55943.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072209-32738.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191014/20191014072210-88401.png)
A.2 | B.6 | C.16 | D.20 |
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