已知等差数列【an】的前n项和为Sn,S4=70 Sn=210 S(n-4)=130,则n
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?
等差数列{an}的前n项和为Sn,且S4=20,Sn-4=60,Sn=120,则n=______.
等差数列{an}的前n项和为Sn,已知S4=S5=-20,若Sn>0则n的最小值为?
已知等差数列{an}的前n项和为Sn,且S4=3,S8=7,则S12=
已知等差数列{an}的前n项和为Sn,若S4=6,S6=4,求S10
已知等差数列{an}的前n项和为Sn,a3=0,S4=-4.
已知等差数列{an}的前n项和为Sn,且(2n-1)Sn+1 -(2n+1)Sn=4n²-1(n∈N*)
设等差数列an的前n项和为Sn,若S4>=10,S5
等差数列{an}的前n项和为Sn,已知S6=36,Sn=324,S(n-6)=144(n>6),则n为多少?
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.
已知等差数列an 的前n项和为sn ,s4=6,s12=18 求s8