题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080112-50170.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080113-39441.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080113-75016.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080113-91957.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080113-97868.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080113-88980.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080114-81425.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080113-97868.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080114-11322.png)
(1)求
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080114-54450.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080114-54798.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080115-24533.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080115-37973.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080115-75174.png)
解析
试题分析:(1)设等比数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080113-97868.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080121-10194.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080121-63490.png)
解得
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080121-49138.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080121-41249.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080121-75580.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080122-94853.png)
(2)由等差数列的前
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080113-75016.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080122-54545.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080122-59228.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080128-92571.png)
---12分
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080113-75016.png)
点评:等差、等比数列经常结合在一起出题,要准确应用其相关公式和性质,另外裂项法是求前
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080113-75016.png)
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080106-74005.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080106-42980.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080106-99428.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080107-74239.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080107-84127.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080107-38586.png)
A.6 | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080058-32144.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080059-96778.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080059-54948.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080059-16633.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080059-26211.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080100-96181.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080048-88039.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080048-50645.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080048-31996.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080049-64628.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080049-42715.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080049-44387.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080049-44387.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080049-42715.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080042-39783.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080043-83077.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080043-11363.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080035-95781.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080035-66853.png)
(1)求通项公式
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080036-31088.png)
(2)设
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080036-26700.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080036-33258.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080036-60093.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012080036-43931.png)
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