已知数列{An}的前n项的和Sn满足6Sn=An^2十3An十2,且An>0.1.求首项A1 2
来源:学生作业帮 编辑:神马作文网作业帮 分类:数学作业 时间:2024/09/26 05:19:13
已知数列{An}的前n项的和Sn满足6Sn=An^2十3An十2,且An>0.1.求首项A1 2
已知数列{An}的前n项的和Sn满足6Sn=An^2十3An十2,且An>0.
1.求首项A1
2.证明{An}是等差数列.
3,求通项公式An
已知数列{An}的前n项的和Sn满足6Sn=An^2十3An十2,且An>0.
1.求首项A1
2.证明{An}是等差数列.
3,求通项公式An
(1)
6Sn=(an)^2+3an+2
n=1
6a1=(a1)^2+3a1+2
(a1)^2-3a1+2=0
(a1-1)(a1-2)=0
a1=1 or 2
(2)
an = Sn -S(n-1)
6an =(an)^2+3an-(a(n-1))^2-3a(n-1)
[an +a(n-1)].[an -a(n-1)-3]=0
an -a(n-1)-3 =0
an -a(n-1)=3
=>{an}}是等差数列, d=3
(3)
an - a1= 3(n-1)
an = 3n-2 or 3n-1
6Sn=(an)^2+3an+2
n=1
6a1=(a1)^2+3a1+2
(a1)^2-3a1+2=0
(a1-1)(a1-2)=0
a1=1 or 2
(2)
an = Sn -S(n-1)
6an =(an)^2+3an-(a(n-1))^2-3a(n-1)
[an +a(n-1)].[an -a(n-1)-3]=0
an -a(n-1)-3 =0
an -a(n-1)=3
=>{an}}是等差数列, d=3
(3)
an - a1= 3(n-1)
an = 3n-2 or 3n-1
已知数列{an}的前n项的和Sn,满足6Sn=an2+3an+2且an>0.(1)求首项a1;(2)证明{an}是
已知数列{an}a1=2前n项和为Sn 且满足Sn Sn-1=3an 求数列{an}的通项公式an
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
已知数列an满足;a1=1,an+1-an=1,数列bn的前n项和为sn,且sn+bn=2
已知数列{an}的前n项和为Sn,且满足an+2Sn+Sn-1=0(n≥2),a1+1/2
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
已知数列{an}满足an>0且对一切n属于正整数,都有a1^3+a2^3+...+an^3=sn^2,sn是{an}的前
已知数列{an}的前n项和为Sn,且满足an+2Sn*Sn-1=0,a1=1/2.
已知数列{An}的前n项和Sn满足2Sn^2=2An*Sn-An (n大于等于2)且A1=2,求An和Sn.
已知数列An的前n项和Sn满足An+2Sn*Sn-1=0,n大于等于2,A1=1/2,求An.
已知数列{an}的前n项和为Sn,且满足Sn=2an-1,n为正整数,求数列{an}的通项公式an
已知数列{an}的前n项和为Sn,且满足Sn=2an-1(n属于正整数),求数列{an}的通项公式an