题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204834-14144.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204835-36816.png)
(1)观察规律,写出数列
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204834-14144.png)
(2)若
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204836-87014.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204836-19418.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204836-79092.png)
(3)设
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204836-34480.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204836-86224.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204836-79829.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204837-19070.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204836-86224.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204834-14144.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204838-47915.png)
(2)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204838-97105.png)
(3)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204838-39884.png)
解析
试题分析:解:①由条件,
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204838-76100.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204839-61469.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204839-92854.png)
故
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204834-14144.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204838-47915.png)
②
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204839-49542.png)
又知
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204839-82153.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204840-28194.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204840-22891.png)
③
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204840-52135.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204840-97987.png)
相减,得
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204841-12643.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204841-78401.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204841-28517.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204838-39884.png)
点评:主要是考查了裂项求和和错位相减法求和的综合运用,属于基础题。
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204508-73285.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204508-63665.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204509-17365.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204509-67150.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204509-50260.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204509-17365.png)
A.19 | B.11 | C.20 | D.21 |
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204444-95419.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204445-56946.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204445-17766.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204444-95419.png)
A.![]() | B.![]() |
C.![]() | D.![]() ![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204304-83316.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204305-17525.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204305-36169.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204304-83316.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204305-63130.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204306-26903.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204306-26903.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009204305-63130.png)
A.18 | B.19 | C.20 | D.21 |
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009203948-99340.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009203948-99340.png)
A.7 | B.8 |
C.10 | D.12 |
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009203910-58487.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009203911-88201.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009203910-58487.png)
A.1 | B.3 | C.5 | D.6 |
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