若a1=3,an+1=3an+3^n+1 1)设bn=an/3^n 证明:数列{bn}是等比数列 (2)求数列{an}的前n项和Sn
来源:学生作业帮助网 编辑:六六作业网 时间:2024/12/21 09:32:19
若a1=3,an+1=3an+3^n+11)设bn=an/3^n证明:数列{bn}是等比数列(2)求数列{an}的前n项和Sn若a1=3,an+1=3an+3^n+11)设bn=an/3^n证明:数列
若a1=3,an+1=3an+3^n+1 1)设bn=an/3^n 证明:数列{bn}是等比数列 (2)求数列{an}的前n项和Sn
若a1=3,an+1=3an+3^n+1 1)设bn=an/3^n 证明:数列{bn}是等比数列 (2)求数列{an}的前n项和Sn
若a1=3,an+1=3an+3^n+1 1)设bn=an/3^n 证明:数列{bn}是等比数列 (2)求数列{an}的前n项和Sn
(1)
a(n+1)=3an+3^(n+1)
a(n+1)/3^(n+1)-an/3^n= 1
{an/3^n} 是等差数列,d=1
an/3^n-a1/3^1=n-1
an/3^n= n
an = n.3^n
(2)
bn = an/3^n = n
{bn}是等差数列
let
S = 1.3^1+2.3^2+...+n.3^n (1)
3S = 1.3^2+2.3^3+...+n.3^(n+1) (2)
(2)-(1)
2S = n.3^(n+1)-(3+3^2+...+3^n)
=n.3^(n+1)- (3/2)(3^n-1)
S = 3 + (6n-3).3^n
Sn = a1+a2+...+an = S = 3 + (6n-3).3^n
数列{an},a1=1,an+1=2an-n^2+3n,求{an}.
a1=1,an+1=an/(3+an),求an=?(n为下标)
an+1 ,n+1是下表 ,an+1=an^3 a1=2 ,求an
数列{an}满足a1=1,且an=an-1+3n-2,求an
在数列an中,a1=2 an+1=an+3n则an=
已知{an}满足a1=1.an=3*n+2An-1,求an
若a1=1,an=3的n次方乘以an-1,求an
已知数列{an}中,a1=1,an+1=3an/(an+3)(N∈N*),求通项an,
数列an满足a1=1/3,Sn=n(2n-1)an,求an
数列{an},a1=3,an*a(n+1)=(1/2)^n,求an
a1=1,an+1=an+3^n-n,求an与sn
在数列{an}中,a1=3,a(n+1)=an+n,求an
已知数列{an}中,a(n+1)=an+2^n,a1=3,求an
在数列{an}中,a1=15,3a(n+1)=3an-2,n属于N*,若an
在{an}中,a1=1,an+1=3an+2n,试求{an}的通项an
数列{an}中,a1=3,an-an*an+1=1(n∈N*),An表示数列{an}的前n项之积,则A2009
已知数列{an}满足a1=4/3,且an+1=4(n+1)an/3an+n
在数列an中,a1=3,an+1=an+1/n(n+1),求通项an?