七年
来源:学生作业帮 编辑:搜搜考试网作业帮 分类:数学作业 时间:2024/07/04 05:18:44
![](http://img.wesiedu.com/upload/c/58/c58d4ee6a5c8ad2fc30ac2f015a5cab5.jpg)
![七年](/uploads/image/z/20313551-47-1.jpg?t=%E4%B8%83%E5%B9%B4)
解题思路: 利用规律求解
解题过程:
解:(1)a5=1/9 ×11=1/2(1/9- 1/11)
(2)an =1/(2n-1)(2n+1) =1/2[1/(2n-1)-1/(2n+1)] (n 为正整数)
(3)a1 +a2+a3+-------+a100
=1/2(1-1/3)+1/2(1/3-1/5)+1/2(1/5-1/7)+-------+1/2(1/199-1/201)
=1/2(1-1/3+1/3-1/5+1/5-1/7+---------+1/199-1/201)
=1/2(1 -1/201)=1/2×200/201 =100/201
最终答案:略
解题过程:
解:(1)a5=1/9 ×11=1/2(1/9- 1/11)
(2)an =1/(2n-1)(2n+1) =1/2[1/(2n-1)-1/(2n+1)] (n 为正整数)
(3)a1 +a2+a3+-------+a100
=1/2(1-1/3)+1/2(1/3-1/5)+1/2(1/5-1/7)+-------+1/2(1/199-1/201)
=1/2(1-1/3+1/3-1/5+1/5-1/7+---------+1/199-1/201)
=1/2(1 -1/201)=1/2×200/201 =100/201
最终答案:略