设Sn是等差数列An的前n项和,若S3/S6=1/3,则S6/S12等于_数学解答

设Sn是等差数列An的前n项和,若S3/S6=1/3,则S6/S12等于

人气：228 ℃　时间：2019-10-11 21:23:23

解答

等差数列S3,S6-S3,S9-S6,S12-S9也成等差数列
S3/S6=1/3,S6=3S3,S6-S3=2S3
S9-S6=3S3,S9=6S3
S12-S9=4S3,S12=10S3
所以S6/S12=3/10