若等差数列{an}的前n项和为Sn,且a2+a3=6,则S4的值为( )
等比数列{an}的前n项和为Sn,且4a1,2a2,a3成等差数列.若a1=1,则S4=( )
等比数列an的前n项和为Sn,且4a1,2a2,a3成等差数列.若a1等于1,则S4为多少?
在公比不为1的等比数列{an}中,前n项的和为Sn,若S2,S4,S3成等差数列,则a2,a4,a3成等差数列.
等比数列{an}的前n项的和为Sn.若4a1.2a2.a3成等差数列,则S4/a4的值是?
等比数列{an}的前n项和为Sn,且4a1,2a3,a3成等差数列,若a1=1,则S4=?
已知sn是公差不为0的等差数列{an}的前n项和,且s1,s2,s4成等比数列,则a1分之a2+a3
设等差数列{an}的前n项和为Sn,若a5=5a3,则S4/S5
记等差数列{an}的前n项和为Sn,已知a2+a4=6,S4=10.
记等差数列{an}的前n项和为Sn,已知a2+a4=6,S4=10.
{An}为等差数列,前n项和为Sn,且S4=-62,S6=-75,求|a1|+|a2|+…+|a14|的值. 解:设Ak
{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?
等差数列{An}的前n项和为Sn,且满足A3*A4=117,A2+A5=22 求通项An ;若数列{Bn}是等差数列,且