1.设等差数列{an}满足:[sin^2(a3)-cos^2(a3)+cos^2(a3)*cos^2(a6)-sin^2(a3)*sin^2(a6)]/sin(a4+a5)=1,公差d∈（-1,0）.若当且仅当n=9时,数列{an}的前n项和Sn取得最大值,则首项a1的取值范围是（）A.(7π/6,4π/3) B.(4π/3,3π

1.设等差数列{an}满足:设等差数列{an}满足:[sin^2(a3)-cos^2(a3)+cos^2(a3)*cos^2(a6)-sin^2(a3)*sin^2(a6)]/sin(a4+a5)=1,公差d∈（-1,0）.若当且仅当n=9时,数列{an}的前n项和Sn取得最大值,则首项a1的取值范围是（）A. 设数列{an}满足an=2an-1+n 若{an}是等差数列,求{an}通项公式 已知递增的等差数列{an},满足a1=1,且a1,a2,a5成等比数列1.求等差数列{an},的通项an2.设bn=an+2^an,求数列｛bn｝的前n项Sn 1.设等差数列{an}满足:[sin^2(a3)-cos^2(a3)+cos^2(a3)*cos^2(a6)-sin^2(a3)*sin^2(a6)]/sin(a4+a5)=1,公差d∈（-1,0）.若当且仅当n=9时,数列{an}的前n项和Sn取得最大值,则首项a1的取值范围是（）A.(7π/6,4π/3) B.(4π/3,3π 1.设等差数列{an}满足:[sin^2(a3)-cos^2(a3)+cos^2(a3)*cos^2(a6)-sin^2(a3)*sin^2(a6)]/sin(a4+a5)=1,公差d∈（-1,0）.若当且仅当n=9时,数列{an}的前n项和Sn取得最大值,则首项a1的取值范围是（）A.(7π/6,4π/3) B.(4π/3,3π 已知数列{an},{bn}满足a1=2,2an=1+2an*an+1,设{bn}=an-1求数列{1n}为等差数列急！！！ 关于数列、等差数列的题目设数列an满足an+1=an-2且a1=241）判断an是什么数列2）若an 已知数列{an}中,满足a1=1,an=2an减1.加.2的n减1次方,设bn=2的n减1次方分之an 证明数列{bn}是等差数列 急 设数列{an}满足：a1+a2/2+a3/3+a4/4……+an/n=An+B,其中A、B为常数.数列{an}是否为等差数列? 设数列an的前n项和为Sn,满足an+sn=An^2+Bn+1(A不等于0)an为等差数列,求(B-1)/A 设正数列a0,a1,a2,…,an,…满足 (n≥2)且a0=a1=1.求{an}的通项公式.设正数列a0,a1,a2,…,an,…满足 (n≥2)且a0＝a1＝1．1.证明√（an/an-1)成等差数列2.求{an}的通项公式． 设等差数列满足an=2an-1+n(n=2,3,.).求通项公式设等差数列满足an=2an-1+n(n=2,3,.)（1）若an是等差数列,求an的通项公式（2）an是否可能为等比数列?若可能,求出此数列通项公式,若不可能,说明理由.过 已知数列{An}的前n项和Sn满足S(n+1)=4An+2(n是正整数）,A1=1.设Cn=An/2n,求证：{Cn}是等差数列. 设等差数列{an}满足a3=5 a10=-9 求{an}的通项公式 已知等差数列an,a2=8,a4=16,数列bn的前n项和Tn满足Tn=2-bn n为正整数 1.求数列an bn的通项公式 2.设...已知等差数列an,a2=8,a4=16,数列bn的前n项和Tn满足Tn=2-bn n为正整数 1.求数列an bn的通项公式2.设cn=an^2* 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 设等差数列{an}的前n项和为Sn,且满足S15>0,S16 已知数列{AN}满足A1=1,AN+1=2AN+2的N次方.[1]设BN=AN/2的N次方,求证：数列{BN}是等差数列；[2]求数列{AN}的通项公式