已知递减的等差数列｛an}满足a1^2=a9^2,则a5=

已知递减的等差数列｛an}满足a1^2=a9^2,则a5= 已知递减的等差数列an满足a1²=a9²,则a5= 已知递减的等差数列{an}满足a1²=a9²,则数列{an}的前n项和Sn取最大值时n= 已知递减的等差数列{an}满足a1=a9,则数列{an}的前n项和Sn取最大值时n= 已知递减的等差数列｛an｝满足a1²＝a9².则数列an的前n项和Sn取最大值时,n＝ 已知等差数列(an)满足a1=2,且a1,a2,a5成等比数列 1.已知递增的等差数列{an}满足a1=1,a3=a2^2-4,则an=? 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:an+1-2an=2^n+1,且a1=2 (1)证明{an/2^n}是等差数列 (2)求数列an的 已知递减的等差数列{an}中,a1^2=a9^2,则Sn取得最大值时,n的值为__________ 已知数列{An}满足A1=1,An+1=2An+2^n.求证数列An/2是等差数列 已知等差数列{an}满足a1=3,a3=-1.(1)求{an}的通项an；(2)求{an}前n项和Sn的最大值 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An 已知数列an满足a1=4 an=4-4/an-1(n大于等于2) 求证bn是等差数列 求数列an的通项公式 已知数列an满足a1=4 an=4-4/an-1(n大于等于2) 求证bn是等差数列 求数列an的通项公式 已知数列｛an｝满足an+an+1=2n+1（n∈N*）,求证：数列｛an｝为等差数列的充要条件是a1=1. 已知数列an满足an+an+1=2n+1(n∈N*).求证数列an为等差数列的充要条件是a1=1 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