等差数列前n项和为Sn,且S9>0,S10

等差数列{an}中,a1>0,前n项和为Sn,且S9>0,S10 等差数列前n项和为Sn,且S9>0,S10 设等差数列{an}的前n项和为Sn,已知a4=12,且S8>0,S9 设等差数列{AN}的前N项和为SN,若S9>0,S10 设等差数列 {an}的前n 项和为Sn,若S9>0 ,S10 已知{an}是等差数列,公差d不等于0,且a1 a3 a13成等比数列,sn是{an}的前n项和,（1）求证s1 s2 s9成...已知{an}是等差数列,公差d不等于0,且a1 a3 a13成等比数列,sn是{an}的前n项和,（1）求证s1 s2 s9成等比数 设等差数列｛An｝的前n项和为Sn,且A5＝5A3,则S9/S5＝? 设等差数列{an}的前N项和为Sn,且a3+a5+a7=15,则S9=? 设等差数列{an}的前n项和为Sn,且a5=3a7,则S9/S13=? 已知等比数列{an}各项为实数且公比为q,前前n项和为Sn,S3,S9,S6成等差数列,求证：a2,a8,a5成等差数列 设Sn为等差数列的前n项和,且S9=18,Sn=240,若an－4=30求项数n 设Sn为等差数列的前n项和,且S9=18,Sn=240,若an－4=30求项数n 等差数列的前n项和为Sn,若S3=S6,则S9=? 已知等差数列前n项和为Sn,S6/S3=3 求S9除S6 等差数列{an}中,已知a1>0,Sn为数列的前n项和,若S9>0,S10 等差数列{an}中,已知a1>0,Sn为数列的前n项和,若S9>0,S10 等差数列{an}的前n项之和为Sn,a3+a8>0,S9 已知等比数列｛αn｝的公比为q(q为实数）,前n项和为Sn,且S3,S9,S6成等差数列,则q3等于什么?