设等差数列{an}的前n和为Sn,若a7/a4=3,则S5/a5的值为
设等差数列{an}的前n项和为Sn,若a5=5a3,则S4/S5
设等差数列[an]的前n项和为Sn,若a5=5a3,则S9/S5等于多少?
设等差数列{an}的前n项和为Sn,且a5=3a7,则S9/S13=?
设Sn是等差数列{an}的前n项和,若a5/a3=5/9,则S9/S5值为?
设等差数列{an}的前n项和为Sn,若S3=9,S5=20,则a7+a8+a9=( )
{an}是等差数列,且a2+a4+a6=-12,a3+a5+a7=-6,如果{an}的前n项和sn取最小值,则n为多少?
设等差数列an的前n项和为Sn,若S4>=10,S5
设Sn是等差数列{an}的前n项和,若a5/a3=5/9,则S9/S5=:
已知等差数列【an】满足:a3=7,a5+a7=26.【an】的前n项和为Sn.(1)求a4及Sn;
已知等差数列{an}满足a3=7,a5+a7=26{an}的前n项和为Sn求a4及Sn
已知等差数列{an},a3=7.a5+a7=26.{an}的前n项和为Sn.1.求a4及Sn.
设{an}是等差数列,{bn}是等比数列,记{an}{bn}的前n项和分别为Sn,Tn若a3=b3,a4=b4,且(S5