已知等差数列按的前n项和为sn,且s2=10,s5=55,则过点P(n,an),Q(n+2,an+2)的直线的斜率

来源：学生作业帮助网编辑：作业帮时间：2024/04/30 03:03:02

已知等差数列按的前n项和为sn,且s2=10,s5=55,则过点P(n,an),Q(n+2,an+2)的直线的斜率
已知等差数列按的前n项和为sn,且s2=10,s5=55,则过点P(n,an),Q(n+2,an+2)的直线的斜率

已知等差数列按的前n项和为sn,且s2=10,s5=55,则过点P(n,an),Q(n+2,an+2)的直线的斜率
S5-S2=a3+a4+a5=45
a3+a5=2a4
所以a4=15
所以a1+3d=15
S2=a1+a2=2*a1+d=10
所以a1=3,d=4
所以k=[a(n+2)-an]/[(n+2)-n]=2d/2=4

已知等差数列{an}的前n项和为Sn,且满足S2=6,a3+a4=22,求an与Sn 一道等差数列题已知：在等差数列{an}中,Sn为前n项和,且S2=16,S4=24.求：S20的值已知等差数列的前n项和为Sn,且满足S3/3-S2/2=1,则数列的公差为多少已知首项为1的等比数列{an}的前n项和为Sn,且S1,S2,S3成等差数列,则Sn等于设等差数列An的前n项和为Sn,且S4=4S2,A2n=2An+1 等差数列{An}的前n项和为Sn,已知S3=a2^2,且S1,S2,S4成等比数列,求{An}的通项公式等差数列{an}的前n项和为{Sn}．已知{S3}=a2²,且{S1},{S2},{S4}成等比数列,求{an}的通项式．等差数列{an}的前n项和为{Sn}．已知{S3}=a22,且{S1},{S2},{S4}成等比数列,求{an}的通项式．等差数列{an}的前n项和为{Sn}．已知{S3}=a22,且{S1},{S2},{S4}成等比数列,求{an}的通项式．等差数列{an}的前n项和为{Sn}．已知{S3}=a2²,且{S1},{S2},{S4}成等比数列,求{an}的通项式．设等差数列{an}的前n项和为Sn,a1=3/2,且S1,S2,S4成等差数列,求Sn 已知等差数列{an}的公差为2,前n项和为Sn,且S1,S2,S4成等比数列．（Ⅰ）求数列{an已知等差数列{an}的公差为2,前n项和为Sn,且S1,S2,S4成等比数列．（Ⅰ）求数列{an}的通项公式；（Ⅱ）令bn=（-1）n-1 已知等差数列按的前n项和为sn,且s2=10,s5=55,则过点P(n,an),Q(n+2,an+2)的直线的斜率等差数列an的前n项和为Sn,已知Sm=a,Sn-Sn-m=b,m、n属于自然数且n>m,求Sn? 等比数列{an}中,前n项和为sn,已知S1,S3,S2成等差数列,求{an}的公比Q.已知a1-a3=3,求sn? 等比数列{an}中,前n项和为sn,已知S1,S3,S2成等差数列,求{an}的公比Q.已知a1-a3=3,求sn?RT. 设等差数列an的前n项和为Sn,a1=3/2,且s1,s2,s4成等比数列,求sn 设等差数列〔an〕的前n项和为Sn,a1=3/2,且S1,S2,S4成等比数列,求Sn.