设数列{an}是首项为a1(a1>0),公差为2的等差数列,其前n项和为Sn,且根号S1,S2,S3成等差数列.求数列{an}的通项公式
人气:414 ℃ 时间:2019-08-19 16:40:50
解答
Sn=a1n+n(n-1)2/2=a1n+n(n-1)2根号S2=根号S1+根号S32根号(2a1+2)=根号a1+根号(3a1+6)4(2a1+2)=a1+3a1+6+2根号a1(3a1+6)8a1+8=4a1+6+2根号a1(3a1+6)4a1+2=2根号a1(3a1+6)2a1+1=根号a1(3a1+6)4a1^2+...
推荐
- 设数列{an}是首项为a1(a1>0),公差为2的等差数列,前n项和为Sn,且根号S1,根号S2,根号S3成等差数列,
- #高考提分#设数列{an}是首项为a1(a1>0),公差为2的等差数列,前n项和为Sn,且根号S1,根号S2,根号S3成等差
- 设数列(an)是首项为a1(a>0),公差为2的等差数列,其前n项和为Sn,且√s1,√s2,√s3
- 设数列{an}的前n项和为Sn,若{an}和{Sn+n}都是公差为d(d≠0)的等差数列,则a1= _ .
- 等差数列{an}中,a1=3,公差d=2,Sn为前n项和,求1/S1+1/S2+…+1/Sn.
- 谁会翻译下面的诗啊?
- 求:以盛名之下,其实难副为题的作文
- 求一一风荷举读后感600字,
猜你喜欢