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

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,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,求S6/S12=? 设Sn是等差数列{An}的前n项和,若S3/S6=1/3,则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? 设Sn是等差数列an的前n项和,若S5/S3=5/9,则S9/S5= 设Sn是等差数列{an}的前n项和,若S3/S6=1/3,则S6/S12=? 设等差数列{an}的前n项和为Sn,若a6=S3=12,则an=多少? 设等差数列{an}的前n项和为Sn,若a6=S3=12,则an=? 设Sn是等比数列{an}的前n项和,S3,S9,S6,成等差数列,则公比q=? 设Sn是等差数列an的前n项和,s6/s12=3/10,则s3/s9=¿ 设Sn是等差数列{an}的前n项和,若a4=9,S3=15,则数列{an}的通项为? 设等差数列的前n项和为Sn,若a6=S3=12,则an=? 设等差数列an的前n项和Sn 若S3=9,S6=36a7+a8+a9=? 设等差数列an的前n项和为sn,若s4/12-s3/9=1,则公差为?