设等差数列{an}的前n项和为Sn,若S4≥10,S5≤15,则a4的最大值为______.
设等差数列{an}的前n项和为Sn,若S4≥10,S5≤15,则a4的最大值为______.
设等差数列an的前n项和为Sn,若S4>=10,S5
设等差数列{an}(n∈正整数)的前n项和为Sn,该数列是单调递增数列,若S4≥10,S5≤15,则a4的取值范围
设等差数列{an}的前n项和为Sn,若a5=5a3,则S4/S5
1.等差数列{an}前n项和为Sn,①S4≥10,S5≤15,求a4最大值;②a(2n)/an=(4n-1)/(2n-1
若Sn是公比为q的等比数列{an}的前n项和,且S4,S6,S5成等差数列,则公比q=______.
设等差数列{an}的前n项和为Sn,若a4≥8,a5≤10,则S6的最小值为______.
设等差数列{an}的公比q=1/2,前n项和为Sn,则S4/a4=
设Sn为等差数列{an}的前n项和,若S5=10,S10=-5,则公差为______(用数字作答).
设Sn为等差数列的{an}的前n项和,已知s3,s4的等比中项是S5,s3,s4的等差中项是1,求an?
设等差数列{an}的前n项和为Sn,若a1>0,S4=S8,则当Sn取得最大值时,n的取值为?
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?