- 注册时间
- 2007-4-26
- 最后登录
- 2013-7-31
- 在线时间
- 2924 小时
- UID
- 2156
- 阅读权限
- 110
- 精华
- 0
- 积分
- 8454
- 帖子
- 14476
- 学币
- 24661
- 学分
- 5559
- 帖子
- 14476
- 学币
- 24661
- 学分
- 5559
- 贡献
- 2
- 贝壳
- 45
- 文采
- 0
|
94年的高数来咯~
[砸死]
The sum of the 1st and 3rd terms of a geometric progression is 2.5.Given that the 1st term is 0.5,find the possible value of the common ratio,r,of the progression.In the case where r>0,determine the last term of the progression which is less than 1000.
T1=0.5
T1+T3=2.5
0.5+ar^2=2.5
0.5+0.5r^2=2.5
0.5r^2=2
r^2=4
r=+2 or -2
Given r>0,
Hence r=2,
...
然后有谁会做么?
我想不到怎样去找last term= =
帮帮忙了谢谢= = |
|