设数列an是等差数列,a1

已知数列an是等差数列,首项a1 设数列an,bn满足:bn=(a1+a2+a3+a4+...+an)/n,若bn是等差数列,求证an也是等差数列 设数列{an}和{bn}满足a1=b1=6,a2=b2=4,a3=b3=3 ,且数列{an+1-an}是等差数列 设数列{an}、{bn}满足：a1=b1=6，a2=b2=4，a3=b3=3，且数列{an+1-an}是等差数列，{bn 设{an}是等差数列,求证以b=(a1+a2+a3+...+an)/n为通项公式的数列{bn}是等差数列 设an是等差数列,求证以bn=(a1+a2+a3+…+an)/n,n属于N+为通项公式的数列bn是等差数列 设数列{an}是等差数列，若a3+a4+a5=12，则a1+a2+…+a7=______． 设数列an为等差数列,数列bn为等比数列若a1 已知数列{an}中a1=-1且(n+1)an,(n+2)an+1(是下标)成等差数列,设bn=(n+1)an-n+2求证 已知数列{an}满足a1=4,an=4-4/an-1(n>=2),设bn=1/an-2(1)求证{bn}是等差数列;(2 设数列{An}{Bn} 满足A1=B1= A2=B2=6 A3=B3=5且{An+1-An}是等差数列{Bn+1-Bn} 设数列{an}的前n项和为Sn,若对任意正整数,都有Sn=n(a1+an)/2,证明{an}是等差数列.