题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101855-91971.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101855-54016.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101855-69577.png)
(I)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101855-54016.png)
(II)设
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101855-44475.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101855-35509.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101856-50133.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101856-87778.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101856-74158.png)
解析
试题分析:(Ⅰ)根据
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101856-97994.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101857-75771.png)
从而通过确定
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101857-18322.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101857-79275.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101857-28610.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101859-12539.png)
(Ⅱ)利用“裂项相消法”求和.难度不大,对基础知识的考查较为全面.
试题解析:(Ⅰ)由已知,
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101856-97994.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101857-75771.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101859-15748.png)
当
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101857-79275.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101859-52778.png)
又
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101859-12539.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101856-87778.png)
(Ⅱ)由(Ⅰ)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101859-63693.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101900-74360.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101900-89342.png)
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101835-17256.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101835-59961.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101835-96894.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101836-17014.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101835-59961.png)
A.5 | B.7 | C.8 | D.7或8 |
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101708-84779.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101708-13427.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101709-86676.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101709-12123.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101709-49042.png)
(Ⅰ)求数列
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101709-43299.png)
(Ⅱ)若数列
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101709-14629.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101710-20707.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101709-14629.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101710-60314.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101710-96362.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101606-91920.jpg)
按照以上排列的规律,第n行(n≥3)从左向右的第3个数为 .
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101445-54153.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101445-47021.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101445-92704.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101446-80842.png)
(1)证明:数列
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101446-91550.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101445-54153.png)
(2)在数列
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101445-54153.png)
(3)若
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101446-13366.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101446-48456.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101447-32476.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101447-41052.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101447-29565.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101447-90574.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101447-27448.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101435-50127.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101435-15639.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101435-94807.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101436-62205.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101436-59714.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101435-94807.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191009/20191009101436-62205.png)
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