| a2n |
| an |
| 4n−1 |
| 2n−1 |
即
| an+nd |
| an |
| 4n−1 |
| 2n−1 |
| 2n−1 |
| 2 |
| d |
| 2 |
Sn＝
| n(a1+an) |
| 2 |
| n2d |
| 2 |
| (2n)2d |
| 2 |
故
| S2n |
| Sn |
故答案为4．
Sn为等差数列{an}的前n项和，若a2nan＝4n−12n−1，则S2nSn=_．
Sn为等差数列{an}的前n项和，若
＝
，则
=______．
| a2n |
| an |
| 4n−1 |
| 2n−1 |
| S2n |
| Sn |
数学人气：634 ℃时间：2020-06-04 19:09:41
优质解答
解析：答 由
＝
，
即
＝
，得an＝
d，a1＝
．
Sn＝
＝
，S2n＝
＝4Sn．
故
=4．
故答案为4．
即
Sn＝
故
故答案为4．
我来回答
类似推荐
猜你喜欢
- 1是talk sth over 还是talk over sth
- 2Your brother has ever heard of the story,_____(反义疑问句)
- 3永不言弃是什么意思
- 4A other than B more than C rather than D better than 这四个答案哪个对?
- 5以"书"为话题的作文
- 6若log(27)12=1/a,则log(6)16=?
- 7以《难忘的一天》为题的作文怎么写?
- 8线性代数 怎么证明0向量等于负的0向量
- 9people wanted Mr.Zhang to see during day the the amimal 单个的词语,练成一句话
- 10英语,what does this word mear?(同意句转换）＿＿ ＿＿ ＿＿of this word?