题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112404-51493.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112404-35592.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112405-37985.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112405-49291.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112405-72363.png)
1)求
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112404-51493.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112405-97296.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112405-37985.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112406-24091.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112404-35592.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112406-46778.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112406-46778.png)
答案
解:1)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112406-82334.png)
2)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112406-55020.png)
解析
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112404-51493.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112407-81385.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112407-58225.png)
∵
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112405-72363.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112407-86364.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112407-29326.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112407-68254.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112408-71019.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112408-91175.png)
得到通项公式。
第二问中,∵
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112408-19285.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112408-26812.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112409-56219.png)
利用错位相减法求和。
解:1) ∵数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112404-51493.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112407-81385.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112407-58225.png)
∵
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112405-72363.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112407-86364.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112407-29326.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112407-68254.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112408-71019.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112408-91175.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112409-52788.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112409-50258.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112408-91175.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112408-71019.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112406-82334.png)
2)∵
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112408-19285.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112408-26812.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112409-56219.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112410-24420.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112410-66441.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112406-55020.png)
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112351-14606.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112352-10152.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112352-52699.png)
1)写出数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112352-39769.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112352-31476.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112352-52699.png)
2)求经过多少年后,该项目的资金可以达到或超过
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112352-71028.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112324-97818.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112324-18133.png)
1)求
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112325-35061.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112325-41397.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112325-70171.png)
3)设
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112325-89819.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112325-35423.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112326-45616.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112309-80368.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112309-60624.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112309-37215.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112310-37751.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112310-46816.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112310-70709.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112254-67251.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112254-36120.png)
(I)证明:数列
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112254-67251.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112254-48558.png)
(II)求
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112255-42659.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112254-67251.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112221-21051.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112221-63353.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112221-21051.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191012/20191012112222-85357.png)
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