设Sn是等差数列{an}的前n项和,若S7=35,则a4=______.
设Sn是等差数列{an}的前n项和,若S7=35,则a4=______.
设Sn是等差数列[an}的前n项和,若S7=5,则a4=
等差数列{an}的前n项和为Sn,若a2+a4+a6=12,则S7的值是______.
来达人~~数列Sn是等差数列An的前n项和 ~~若A7/A4=2则 S13/S7=?2.等差数列An中 A1+A4+A1
已知Sn为等差数列{an}的前n项和,若a2:a4=7:6,则S7:S3等于______.
设Sn是等差数列{an}的前n项和,若S7等于35,则a4等于?解题思路也写一下
设Sn是等差数列{an}的前n项和,已知a2=3,a6=11,则S7=______.
设Sn是等差数列{an}的前n项和,若a4=9,S3=15,则数列{an}的通项为______.
设等差数列{an}的前n项和为Sn,a3 a4=8,S7=5a5(1)求an通项公式(2)若bn=
设等差数列{an}的前n项和为Sn,a3+a4=8,S7=5a5 (1)求an通项公式 (2)若b
设Sn是等差数列{an}的前n项和,已知a2=3,S11=121,则S7=
设Sn是等差数列an的前n项和,已知a2=3,S11=121,则S7等于