题目
题型:江西省月考题难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021547-12606.png)
(Ⅰ)求a2,a3,a4;
(Ⅱ)猜想数列{an}的通项公式,并证明你的结论;
(Ⅲ)已知数列{bn}满足:anbn=1﹣an,Sn为数列{bn}的前n项和,证明:S1+S2+…+Sn﹣1=n(Sn﹣1)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021547-39047.png)
∴n=1时,2a2=a1a2+1,∴
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021548-45209.png)
n=2时,2a3=a2a3+1,∴
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021548-18380.png)
n=3时,2a4=a3a4+1,∴
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021548-88498.png)
(Ⅱ)猜想数列{an}的通项公式
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021548-90358.png)
证明:①当n=1,2,3,4时,由(Ⅰ)知结论成立;
②假设n=k时,结论成立,即
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021548-41100.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021549-16161.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021549-13091.png)
即n=k+1时,结论成立
由①②可知
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021549-57020.png)
(Ⅲ)解:由anbn=1﹣an,可得
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021550-32124.png)
∴S1+S2+…+Sn﹣1=(n﹣1)+
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021550-44218.png)
=n+
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021550-10251.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021550-42187.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021550-63154.png)
=n(1+
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021551-97757.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021551-19361.png)
=n(Sn﹣1)
核心考点
试题【已知数列{an}满足:,2an+1=anan+1+1(Ⅰ)求a2,a3,a4;(Ⅱ)猜想数列{an}的通项公式,并证明你的结论;(Ⅲ)已知数列{bn}满足:an】;主要考察你对数列综合等知识点的理解。[详细]
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021413-25541.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021413-39268.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191015/20191015021414-72716.png)