记等差数列{A}的前n项和为s若A1等于二分一.s4等于20则s6等于多少?
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?
设等差数列前n项和为Sn,若a1=0.5,S4=20,则S6为
设等差数列{an}的前n项和为Sn,若S2=4,S4=20,则该数列的公差d等于多少?
设Sn是等差数列An的前n项和,若S3/S6=1/3,则S6/S12等于
设Sn是公差不为0的等差数列an地前n项和且S1,S2,S4成等比数列,则a1/a2等于
Sn是等差数列an的前n项和,若S6=36,Sn=324,S(n-6)=144(n>6),则n等于?
已知等比数列{an}的公比为q,前n项的和为Sn,且S3,S9,S6,成等差数列,则q的三次方等于多少,
设Sn为等差数列{an}的前n项的和,已知S4=22,S(n-4)=92,Sn=210(n>4),则n等于多少?
设Sn是等差数列{an}的前n项和,若S3/S6=1/3,则S6/S12等于——
设Sn是等差数列{an}的前n项和,若S8/S4 =3,则S16/S8等于多少,为什么
已知等差数列{an}的前n项和为Sn,若S4=6,S6=4,求S10
已知等比数列{αn}的公比为q(q为实数),前n项和为Sn,且S3,S9,S6成等差数列,则q3等于什么?