题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043806-87285.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043806-50831.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043806-40133.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043806-25547.png)
解析
试题分析:
解析:由
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043807-97562.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043807-44701.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043807-34185.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043806-40133.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043806-25547.png)
点评:等差数列中的基本问题。研究等差数列中前n项和的最值问题,通常与二次函数结合在一起。也可以考查数列的增减性、正负项分界情况,明确何时使前n项和取到最值。
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043643-91995.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043644-17630.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043644-93265.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043643-91995.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043644-87373.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043532-26092.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043532-72202.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043532-13581.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043532-26092.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043532-15744.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043533-95359.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043532-72202.png)
(2)设
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043533-38295.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043533-23372.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043532-15744.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043533-53629.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043458-80635.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043458-93587.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043458-39510.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043458-79776.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043458-80635.png)
(2)设
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043459-19034.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043459-47045.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043458-93587.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043459-98354.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043340-19358.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043340-69995.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043340-32140.png)
(1)求
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043340-12438.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043341-85925.png)
(2)设
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043341-58689.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043341-74555.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043312-23839.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043313-41062.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043313-70320.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191010/20191010043313-53778.png)
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