若数列{an}为等差数列 求证 数列{2的an次方}为等比数列 现在要啊 快啊

若数列{an}为等差数列 求证 数列{2的an次方}为等比数列 现在要啊 快啊 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 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. 两个数列{an}和{bn}满足bn=a1+2a2+...+nan/1+2+...+n,求证：若{bn}为等差数列,则数列{an}也是等差数列?能看懂的 若数列{an}的前n项和为Sn=an^2+bn+c,求证数列{an}为等差数列的充要条件是c=0 已知数列{an}的前n项和为Sn=n^2-3n,求证：数列{an}是等差数列 已知数列﹛an}的通项公式为4-2n,求证：数列﹛an}是等差数列 数列{an}为等差数列(d 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满足 a1=1/2,an+1=3an/an+3求证1/an为等差数列已知数列an满足 a1=1/2,an+1=3an/an+3求证1/an为等差数列 已知数列{an}满足a1=2,an+1=2an/an+2.求证数列{1/an}是否为等差数列 并求出an 已知数列{lgan}是首项为3,公差为2的等差数列,求证:{an}是等比数列. 已知数列{an}中,an=7^n+2,求证:数列{lgan}是等差数列 已知数列{an}中,an>0其前n项和为Sn,且Sn=1/8(an+2)²,求证：数列{an}为等差数列 数列an,a1＝2,an＝2a(n-1)+2n次（n≥2）（1）求证数列an/2n是等差数列（2）求数列an的前n项和Sn（3）若bn=2n-1/an,求证数列bn为递减数列 数列 (30 20:12:4)设两个数列{An},{Bn}满足Bn=（a1+2*a2+3*a3+…+n*an）/（1+2+3+…+n）,若{Bn}为等差数列,求证：{An}也为等差数列 在等比数列{an}中,an＞0,n属于N*：若{bn}是等差数列,求证数列{lg an}是等差数列,数列{2bn}是等比数列 数列{an}中a1=2,an+1=an+2的n次方+1,求证数列{an-2的n次方}为等差数列