已知数列{an}为等差数列,求证:{a3n+a3n-1}是等差数列.

已知数列{an}和{bn}满足关系:bn=(a1+a2+a3+…+an)/n,(n∈N*).若{bn}是等差数列,求证{an}为等差数列 已知数列{an}为等差数列,且a1=2,a1+a2+a3+=12,求证数列{bn}是等比数列令bn=3的an次方 已知数列{An}为等差数列,且A1=2,A1+A2+A3=12.令Bn＝3^(An),求证：数列{Bn}是等比数列 已知数列{an}为等差数列,且a1=2,a1+a2+a3=12,令bn=3^an,求证,数列{bn}是等比数列 已知数列｛lg an｝为等差数列,求证｛an ｝是等比数列已知数列｛lg a 已知数列an中a3=2,a7=1,且数列1/（an+1)为等差数列求an 高一数学等差数列已知数列｛an｝和｛bn｝满足 bn=(a1+2*a2+3*a3+...+na4)/(1+2+3+...+n),求证：｛an｝为等差数列时｛bn｝必为等差数列；反之亦然.帮帮忙,做对的可以加分 已知数列an为等差数列,an=n,则a1*a2-a2*a3+a3*a4-a4*a5+...-a100*a101= 已知{An}为等差数列,Bn=A3n+1,求证数列Bn为等差数列. 数列{an}{bn}满足bn=a1+2a2+3a3+…+nan/(1+2+3+…+n),若数列{an}为等差数列,求证；{bn}为等差数列. 若数列{an},{bn}都是等差数列,s,t 为已知常数,求证数列{ s an+t bn}是等差数列 已知数列an中 a3=2 a7=1 又数列1/an+1 为等差数列 则a11等于 已知数列{an}中,a3=2,a7=1,又数列{1/an+1}为等差数列,则a11, 已知数列{an}为等差数列,求证:{a3n+a3n-1}是等差数列. 已知{an}为等差数列,a3+a8=22,a6=7,则a5=【数列问题】 已知数列[An]为等差数列,a1+a3+a5=17,a4=7,则S6= 已知数列{an}满足a1+a/4,(1-an)a(n+1)=1/4,令bn+an-1/2 求证数列{1/bn}为等差数列,求和:Sn=a2/a1+a3/a2+...+a(n+1)/an已知数列{an}满足a1=1/4,(1-an)(a(n+1))=1/4,令bn=an-1/2 求证数列{1/bn}为等差数列，求和:Sn=a2/a1+a3/a2+... 已知数列{an}和{bn}满足bn=a1+2a2+3a3+L+nan/1+2+3+L+n,求证：{an}为等差数列时{bn}必为等差数列；反而亦然