已知等差数列an的前n项和为Sn,满足S8=20,且知首项与公差互为相反数,则a1=
1.已知等差数列的{An}前n项和为sn,且s5=40,s8=100,求a1和公差d?2.已知等差数列{An}中,a1=
已知等差数列{an}的前n项和为Sn,且S4=3,S8=7,则S12=
已知等差数列{an}的公差d不为零,首项a1=2且前n项和为sn
已知等差数列{An}的前n项和为Sn,a1+a3+a6+a8=10求S8的值
设Sn为等差数列{an}的前n项和,已知a9=-2,S8=2 (1)求首项和公差 (2)当n为何值,Sn最大?
等差数列{an}的前n项和为Sn,且S3=6,a1=4,则公差d等于
已知数列{an}的前n项和为Sn,且满足an+2Sn*Sn-1=0,a1=1/2.求证:{1/Sn}是等差数列
已知等差数列{An}的前n项和为Sn,若A3=20-A6,则S8等于多少?
已知数列{an}的前n项和为Sn,且满足Sn=Sn-1/2Sn-1 +1,a1=2,求证{1/Sn}是等差数列
设等差数列{an}的前n项和为Sn,已知a4=12,且S8>0,S9
已知等差数列{an}中,公差d>0,其前n项和为sn,且满足a2a3=45,a1+a4=14
已知等差数列{an}中,公差d>0,其前n项和为Sn,且满足a2×a3=45,a1+a4=14