设各项均为正数的数列{an}的前n项和为Sn已知2a2=a1+a3数列{根号Sn}的公差为d的等差数列
求数列{an}的通向公式（用n,d表示）
人气：479 ℃ 时间：2019-08-19 23:44:16
解答
{根号Sn}的公差为d的等差数列 √Sn=√S1+(n-1)d Sn=[√S1+(n-1)d ]^2=S1+(n-1)^2d^2+2√S1(n-1)dS2=S1+d^2+2√S1dS3=S1+4d^2+4√S1da1=S1a2=S2-S1= d^2+2√S1da3=S3-S2=3d^2+2√S1d2a2=a1+a3即2d^2+4√S1d=S1+3d^2+2...
推荐
- 设各项均为正数的数列｛an｝的前项和为sn,已知2a2=a1+a3,数列｛根号sn｝是公差为2的等差数列,
- 设各项均为正数的数列｛an｝的前n项和为Sn,已知2a1=a1+a3,数列｛根号下Sn｝是公差为2的等差数列
- 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,
- 已知根号x,[根号f(x)]/2,根号3（x大于等于0）成等差数列.又数列｛an｝(an>0)中,a1=3,此数列前n项和Sn对
- 设f(x)=x3,等差数列｛an｝中a3=7,a1+a2+a3=12,记Sn=f（三次根号（an+1））,令bn=anSn,数列｛1/bn｝的
- 制热功率 1450+1050 啥意思
- 与三国故事有关的成语或俗语
- There was no_____of the diagreement between the two neighbouring countries in the newspaper.
猜你喜欢
