sn等差数列an的前n项和s3=6 s6=24求a9

等差数列(an)的前n项和sn,若s6：s3=3,求s9：s6 sn等差数列an的前n项和s3=6 s6=24求a9 等差数列{ an}的前n项和Sn,S3=S6,则S9=? 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S3/S6=1/3,求S6/S12=? 设Sn是等差数列{An}的前n项和,若S3/S6=1/3,则S6/S12=? 等差数列an的前n项和为sn若s6/S3=3,则s9/S6=? 设等差数列{an}的前n项和为Sn,若S6/S3=3,则S9/S6=? 设Sn是等差数列{an}的前n项和,若S3/S6=1/3,则S6/S12=? 设Sn是等差数列An的前n项和,若S3/S6=1/3,则S6/S12等于 设Sn是等差数列{an}的前n项和,若S3/S6=1/3,求S6/S12 1.设Sn是等差数列【An]的前n项和,若S3/S6=1/3,求S6/S12 设Sn是等差数列{an}的前n项和,若S3/S6=1/4,则S6/S12等于? 已知等比数列{an}的前n项和为Sn,若S3,S9,S6成等差数列,则 A S6=-1/2xS3 B S6=-S3 C S6=1/2xS3 D S6=2S3 设Sn是等差数列an前n项和 若S3/S6=1/3则S6/S12正确的做法我知道 但我这种做法怎么错了Sn成等差 所以S3,S6-S3,S12-S6也成等差因为S3/S6=1/3,所以S6-S3=2S3,所以S12-S6=3S3所以S12=6S3 所以S6/S12=1/2 Sn是等差数列an前n项和,若S3/S6=1/3,则S6/S12=? sn是等差数列｛an}前n项和,若s3/s6=1/3,求s6/s12 设等差数列an的前n项和Sn 若S3=9,S6=36a7+a8+a9=?