设Sn是等差数列an的前n项和,若S7=a5+a9,则a4\a7?A 1\3 B 2\7 C 1\2 D 1

设Sn是等差数列an的前n项和,若S3/S7=1/3,则S6/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,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,若S7=35,则a4为几? 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,已知a2=3,S11=121,则S7等于 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? 设等差数列an的前n项和为Sn,若S7=49,a6=11,则a2= 设等差数列 An的前n 项和Sn为 ,若a7=7a4 ,则S13/S7 = {an}是等差数列,前n项和为Sn,若a3=18-a4,求S7 请问数学题,设Sn是等差数列｛An｝的前n项和,若a7/a4=2,则S13/S7的值为? 设Sn是等差数列(an)的前n项和,已知a2等于3,a6等于11,则S7等于 设Sn为等差数列an的前n项和,S4=14,S10-S7=30,则S9=