等差数列{an}的前n项和为Sn,公差d

等差数列{an}的前n项和为Sn,公差d 记数列{an}的前n项和为Sn,若{Sn/an}是公差为d的等差数列,则{an}为等差数列的充要条件是d=? 已知等差数列an的公差为d,前n项和Sn＝－n^2,则通项公式为 设等差数列{an}公差d是2,前n项和为Sn,则lim(an^2-n^2)/Sn 设等差数列{an}公差d是2,前n项和为Sn,则lim(an^2-n^2)/Sn 等差数列｛an｝前n项和为Sn,且Sn=3n^2+n 求公差d 设公差为d的等差数列{an}的前n项和为Sn,若a1=1,-2/17 设数列{an}的前n项和为Sn,若{an}和{根号sn+n}都是公差为d的等差数列,则a1= 谢谢）在等差数列{an}中,设公差为d,若前n项和Sn=-n²;,则{an}的通项公式和公差分别 设等差数列an的公差d为2,前n项和为Sn,则lim(an^2-n^2)/Sn=? 等差数列 an的前n项和为sn ,若s2=4,s4=20,则公差d= 等差数列｛An｝的前n项和为 Sn,且S3＝6,A1＝4,则公差d＝? 设Sn为等差数列{an}的前n项和,S5=10,S10=-5,则公差d=? 设等差数列{an}的前n项和为Sn 已知S3=S12 则当公差d 等差数列｛an｝的前n项和为Sn,且S3=6,a3=4.求公差d=? 设等差数列的公差d为2,前n项和为Sn,则lim(n→∞)(an^2-n^2)/Sn 已知等差数列{an}公差为d(d≠0),前n项和为Sn,Xn表示{an}前n项的平均数,且数列｛Xn｝补充如下：已知等差数列{an}公差为d(d≠0),前n项和为Sn,Xn表示{an}前n项的平均数,且数列｛Xn｝的前n项和为Tn,且数 已知{an}是公差d等差数列,已知它的前n项和为Sn,S4=2S2+4,则公差d为多少