等差数列{an}前n项和为Sn,若a7+a9=16,S7=7,则a12=______.
设等差数列{an}的前n项和为Sn,若S3=9,S6=36,则a7+a8+a9=______.
已知等差数列{an}前n项和为Sn,且a3+a8=13,S7=35,则a7=______.
在等差数列{an}中前n项和为Sn,若a7=5,S7=21那么S10=
设Sn是等差数列{an}的前n项和,若S5=a8+5,S6=a7+a9-5,则公差d等于______.
设Sn是等差数列an的前n项和,若S7=a5+a9,则a4\a7?A 1\3 B 2\7 C 1\2 D 1
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,S7=3(a2+a12),则a7a4的值为( )
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
设Sn是等差数列{an}的前n项和,若S7=35,则a4=______.
设Sn为等差数列{an}的前n项和,S8=4a3,a7=-2,a9=?
设等比数列{an}中,前n项和为Sn,已知S3=8,S6=7,则a7+a8+a9=______.
设等差数列{an}的前n项和为Sn,若S3=9,S5=20,则a7+a8+a9=( )