数列{an},a1=2,an+1(下标)=an下标+n+1 求通项an下标

来源:学生作业帮助网 编辑:六六作业网 时间:2024/12/23 01:21:19
数列{an},a1=2,an+1(下标)=an下标+n+1求通项an下标数列{an},a1=2,an+1(下标)=an下标+n+1求通项an下标数列{an},a1=2,an+1(下标)=an下标+n+

数列{an},a1=2,an+1(下标)=an下标+n+1 求通项an下标
数列{an},a1=2,an+1(下标)=an下标+n+1 求通项an下标

数列{an},a1=2,an+1(下标)=an下标+n+1 求通项an下标
根据题意有:
a2-a1=2;
a3-a2=3;
a4-a3=4;
...
a(n)-a(n-1)=n+1;
各项相加得:
a(n)-a1=2+3+4+...+n=(n-1)(n+2)/2;
a(n)=(n-1)(n+2)/2+2=(n^2+n+2)/2;

an=n*n+1

根据你的题目条件,有下列式子成立:
a1=1 +1
a2=a1+2
a3=a2+3
a4=a3+4
.....
an=a(n-1)+n
把这些式子相加,左边和左边加,右边和右边加,可得:
a1+a2+a3+...+a(n-1)+an=1+a1+a2+a3+...+a(n-1)+[1+2+...+n]
整理得:
an=1+(n)(n+1)/2

无通项

数列{an},a1=2,an+1(下标)=an下标+n+1 求通项an下标 知数列{an}满足a1=-2,an+1(下标)=2+2an/(1-an),则an为? 已知数列{an}满足a1=-2,an+1(下标)=2+2an/(1-an),则a4= 数列{an}(n下标),a1=8,a4=2,且满足an+2(n+2下标)=2an+1(n+1下标)-an(n下标).设·Sn=|a1|+|a2|+|an|,求Sn 数列{an}(n下标),a1=8,a4=2,且满足an+2(n+2下标)=2an+1(n+1下标)-an(n下标).求数列{an的通项公式 数列{an}中,a1=2,an+1=4an-3n+1,求证{an-n}是等比数列 4an中n为下标an+1中n+1为下标an-n中an的n为下标 已知数列{an},a1=1,a下标(n+1)=1+(1/2)an,求an 用等比数列 数列an中,a1=1,2an+1-2an=3,则通项an=n是下标,2后跟的是an+1和an次方 已知数列an中 a1=-2且an+1=sn(n+1为下标),求an,sn 已知在数列{an}中,a1=2,an=3a[(n-1)](下标)-2,求an 在数列{an}中,a1=3,an=3an+1(an+1为下标),则an=? 数列{an}满足a1=2,an+1=(1+an)/(1-an) ,n+1,n为下标,n属于N*,则a1*a2*a3*.*a2010的值? 若数列an满足a1=1,an+1(+1下标)=1/2an + 1(1/2an与+1分开),求an 在数列an中,a1=1,an=3an-1-1/2=3^n,求an(3an-1里头n-1是下标.) 在数列an中,已知a1=-1,(an+1)*an=(an+1)-an(n均为下标),则数列an的通项an= 已知数列{an(n下标)}满足a1(1下标)=1,a2(2下标)=3,.求证:bn(n下标)是等差数列.已知数列{an(n下标)}满足a1(1下标)=1,a2(2下标)=3,an+2(n+2下标)=3an+1(n+1下标)-2an (n下标) (n∈N 已知数列{an}满足:a1=1,且an-an-1=2n,求(1)a2,a3,a4.(2)求数列{an}的通项anan都是a的下标n,an-1是a的下标n-1 已知数列{an}中a1=1,an+1(下标是n+1)=an+2an/an+2(下标是n).求这个数列的通项公式