大师作文网已知数an=4n-1,bn=(1/n)(a1+a2+.+an).设bn的前n项和为sn,则lim（1/s1 + 1/s2
来源：学生作业帮 编辑：大师作文网作业帮 分类：数学作业 时间：2024/11/18 03:57:48
已知数an=4n-1,bn=(1/n)(a1+a2+.+an).设bn的前n项和为sn,则lim（1/s1 + 1/s2 +.+ 1/sn)=多少?
a1+a2+...+an=-n+2n*(n+1)=2n^2+n
bn=2n+1
sn=n+n(n+1)=n^2+2n=n(n+2)
1/sn=1/[n(n+2)]=0.5*(1/n-1/(n+2))
极根=lim 0.5*(1-1/3+1/2-1/4+1/3-1/5+1/4-1/6+...+1/(n-1)-1/(n+1)+1/n-1/(n+2))
=lim 0.5*(1+1/2-1/(n+1)-1/(n+2))
=0.5*3/2=3/4
bn=2n+1
sn=n+n(n+1)=n^2+2n=n(n+2)
1/sn=1/[n(n+2)]=0.5*(1/n-1/(n+2))
极根=lim 0.5*(1-1/3+1/2-1/4+1/3-1/5+1/4-1/6+...+1/(n-1)-1/(n+1)+1/n-1/(n+2))
=lim 0.5*(1+1/2-1/(n+1)-1/(n+2))
=0.5*3/2=3/4
数列an的通式为an=4n-1,令bn=a1+a2+..+an/n则数列bn的前n项和为?
等差数列{an},{bn}的前n项和分别为An,Bn,切An/Bn=2n/3n+1,求lim(n→∞)an/bn
设数列an前n项和Sn已知a1=a2=1 bn=nSn+（n+2）an数列bn公差为d的等差数列n属于N...
已知数列{an}的前n项和为sn,4sn=an+1(n属于N),(1)求a1,a2 (2)设bn=log3/an/,求数
设等差数列{an}的前n项和为Sn，等比数列{bn}的前n项和为Tn，已知bn＞0（n∈N*），a1=b1=1，a2+b
设数列{an}的前n项和为Sn,已知a1=a,an+1=Sn+3^n,n∈N+.设bn=Sn+3n,求数列{bn}的通项
设数列{an}的前n项和为sn,已知a1=a,an+1=sn+3^n,n∈N* (1)设bn=sn-3^n,求数列{bn
设数列{an}的前n项和为sn.已知a1=a,an+1=sn-3n,n∈N*,设bn=sn-3n,且bn≠0
等差数列an,bn的前n项和分别为Sn,若Sn/Tn=2n/(3n+1),求lim an/bn
已知正数等差数列an满足a1+a6=a2(a3-1),公比为q的等比数列Bn的前n项和Sn满足2S1+S3=3S2,a1
数列an的前n项和为Sn=2^n-1,设bn满足bn=an+1/an,判断并证明bn 的单调性
a1+a2+a3=-6 a1*a2*a3=64 bn=(2n+1)*an 求数列{bn}的前n项和 sn的通向公式