设等差数列an的前n项和为Sn,若a5=5a3,则S9/S5=?

设等差数列{An}的前n项和为Sn,若A5=5A3,则S9/S5=? 设等差数列{an}的前n项和为Sn,若a5=5a3,则S9/S5=? 设等差数列｛AN｝的前N项和为SN,若A5=5A3则S9/S5=?. 设等差数列an的前 n项和为Sn ,若S9=81 ,则a2+a5+a8=? 设等差数列an的前n项和为Sn,若a5=5a3,则S9/S5=? 设等差数列{An}的前n项和为Sn,若A2+A8=15-A5,则S9等于? 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,若S9=72,则a1+a5+a9等于多少? 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S9＝72,则A2+A5+A9＝? 设等差数列{an}的前N项和为Sn,且a3+a5+a7=15,则S9=? 设等差数列{an}的前n项和为Sn,且a5=3a7,则S9/S13=? 设等差数列｛an｝前n项和为Sn,若a1=-9,a3+a5=-6 设等差数列{an}的前n项和为Sn,a3 a4=8,S7=5a5(1)求an通项公式(2)若bn=设等差数列{an}的前n项和为Sn,a3 a4=8,S7=5a5(1)求an通项公式(2)若bn=an,n<=21/Sn 设等差数列{an}的前n项和为Sn 若a1=Sn> 设Sn是等差数列an的前n项和,若a5/a3=5/9,则S9/S5= 设sn是等差数列{an}的前n项和,若s9/s5=9/5,则a5/a3=