设Sn是等差数列an的前n项和,若S3/S7=1/3,则S6/S7=

问题描述:

设Sn是等差数列an的前n项和,若S3/S7=1/3,则S6/S7=

S3/S7=1/3
3﹙3a1+3q﹚=7a1+21q
a1=6q
S6/S7=﹙6a1+15q﹚/﹙7a1+21q﹚=51/63=17/21