已知等差数列{an}的前n项和为Sn,且满足S6=42,a5+a7=24.
已知等差数列{an}的前n项和为Sn,且满足S6=42,a5+a7=24 (1)求数列{an}的通项an及前n项和Sn.
已知等差数列{An}满足:a3=7 ,a5+a7=26 ,{An}的前n项和为Sn
已知等差数列{an}满足:a3=7,a5+a7 =26,an的前n项和为sn.
已知等差数列{an}满足:a3=7,a5+a7=26.{an}的前n项和为Sn.
已知等差数列an满足a3=7,a5+a7=26,an的前n项和为sn.1.求an和sn
已知等差数列{an}满足:a3=7,a5+a7=26,{an}的前n项和为Sn.求an及Sn.
已知等差数列【an】满足:a3=7,a5+a7=26.【an】的前n项和为Sn.(1)求a4及Sn;
已知等差数列{an}满足a3=7,a5+a7=26{an}的前n项和为Sn求a4及Sn
已知等差数列(an)满足:a3=7,a5+a7=26,(an)的前n项和为Sn
已知{an}是等差数列,前n项和是Sn,且a2+a7=9,S6=7a3.
(2014•东营二模)已知数列{an}为等差数列,且a5=14,a7=20,数列{bn}的前n项和为Sn,且满足3Sn=
设等差数列{an}的前n项和为Sn,且a5=3a7,则S9/S13=?