题目内容
(6分)观察下列有规律的数:
,
,
,
,
,
……根据规律可知
(1)第7个数_____________,第n个数是______________(n是正整数)
(2)
是第__________个数
(3)计算![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408230055245761450.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823005524467343.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823005524482341.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823005524498368.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823005524513411.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823005524529407.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823005524529413.png)
(1)第7个数_____________,第n个数是______________(n是正整数)
(2)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823005524545440.png)
(3)计算
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408230055245761450.png)
(1)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823005524591415.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823005524607571.png)
(2)11
(3)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823005524607521.png)
此题考查寻找规律
思路:
,由此可以观察出第n个数为![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823005524607571.png)
(1) 第7个数,令n=7,
,第n个数为![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823005524607571.png)
(2) 令![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408230055246851834.png)
(3)![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408230055247012987.png)
答案 (1)
,
(2)11 (3)![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823005524607521.png)
思路:
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408230055246231923.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823005524607571.png)
(1) 第7个数,令n=7,
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823005524654998.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823005524607571.png)
(2) 令
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408230055246851834.png)
(3)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/201408230055247012987.png)
答案 (1)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823005524591415.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823005524607571.png)
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823005524607521.png)
![](http://thumb.zyjl.cn/images/loading.gif)
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