已知等差数列An的前n项和为Sn,且S13>0,S14
已知等差数列an的前n项和为sn,且s13>s6>s14,a2=24①求公差d的取值范围②问数列{sn}是否存在最大项
设等差数列{an}的前n项和为Sn,已知a3=12,且S12>0,S13
已知等差数列{an} 的前n项和为Sn,若S12>0,S13
设等差数列{an}的前n项和为Sn,已知S12>0,S13
设等差数列{an}前n项和为Sn,且a1>0,S13=S19,求Sn的最大值
等差数列an ,前n项和为Sn,a1>0,且s12>0,s13
等差数列{an}的前n项和Sn已知a3=12,S12>0,S13
设等差数列{an}的前n项的和为Sn,已知a3=12,S12>0,S13
设等差数列{an}的前n项和为Sn,已知a3=12,S12>0,S13<0
设等差数列an的前n项和为sn已知a3=12 s12大于0 s13小于0
设等差数列{an}的前n项和为Sn,已知a3=12,S12>0,S13
设等差数列{an}的前n项和为Sn,已知a3=12,S12>0,S130,S13