Sn是等差数列{an}的前n项和,S7=3(a3+a7),那么S9/a4=?

设Sn是等差数列an的前n项和,若S3/S7=1/3,则S6/S7= {an}是等差数列,前n项和为Sn,若a3=18-a4,求S7 等差数列｛an｝的前n项和为Sn,则(S7-S3)/S10=? 已知等差数列{an}的前n项和为Sn,则S7-S3除以S10= 等差数列an的前n项和为sn 且s7=7 则a2+a6 设Sn是等差数列 an 的前n项和,S7=3(a3+a7),求a5/a4的值 设Sn是等差数列{an}的前n项和,已知a2=3,a6=11,则S7=? 设Sn是等差数列｛an｝的前n项和,已知a2=3,S11=121,则S7= 设Sn是等差数列｛an｝的前n项和,若S7=35,则a4= 有人吗 设Sn是等差数列an的前n项和,已知a2=3,S11=121,则S7等于 Sn是等差数列{an}的前n项和,S7=3(a3+a7),那么S9/a4=? 设Sn是等差数列an的前n项和,若S3/S6=1/3,则S6/S7=? 设Sn是等差数列[an}的前n项和,若S7=5,则a4= 设Sn是等差数列｛an｝的前n项和,已知a1=3,a2=11,则S7等于? 设Sn是等差数列 an 的前n 项和,已知a2=3,a6=11,求S7. 设Sn是等差数列｛an｝的前n项和,已知a2=3,a6=11,则S7等于? 设Sn是等差数列{an}的前N项和,若S7=35,则a4为几? {an}是等差数列 S7=7 S15=75 Tn是数列{Sn/n}的前n和 求Tn