高二数列题:设数列{an}满足an+1=an^2-nan+1,n为正整数,当a1>=3时,证明……
来源:学生作业帮 编辑:搜搜考试网作业帮 分类:数学作业 时间:2024/05/30 17:22:29
高二数列题:设数列{an}满足an+1=an^2-nan+1,n为正整数,当a1>=3时,证明……
设数列{an}满足an+1=an^2-nan+1,n为正整数,当a1>=3时,证明
(1)an>=n+2
(2)1/(1+a1) + 1/(1+a2) + ……+1/(1+an) =< 1/2
设数列{an}满足an+1=an^2-nan+1,n为正整数,当a1>=3时,证明
(1)an>=n+2
(2)1/(1+a1) + 1/(1+a2) + ……+1/(1+an) =< 1/2
(1)当n=1时,a1>=3=1+2,an>=n+2成立;
当n >1时,an=(an-1)^2-nan-1+1,令S= an-(n+2)
=(an-1)^2-nan-1+1-(n+2)
=(an-1)^2-(n+1)an-1-1.
我们把S看作是以an-1为变数的二次函数,其中,
二次项系数=1大于0,
△=[-(n+1)]^2-4*1*(-1)= (n+1)^2+4>0,因此,S>0,
即an>n+2成立.
结合a1>=3有,an>=n+2成立.
当n >1时,an=(an-1)^2-nan-1+1,令S= an-(n+2)
=(an-1)^2-nan-1+1-(n+2)
=(an-1)^2-(n+1)an-1-1.
我们把S看作是以an-1为变数的二次函数,其中,
二次项系数=1大于0,
△=[-(n+1)]^2-4*1*(-1)= (n+1)^2+4>0,因此,S>0,
即an>n+2成立.
结合a1>=3有,an>=n+2成立.
高二数列题:设数列{an}满足an+1=an^2-nan+1,n为正整数,当a1>=3时,证明……
设数列{An}满足An+1=An^2-nAn+1,n为正整数,当A1>=3时,证明对所有的n>=1,有
设数列{an}满足:an+1=an^2-nan+1,n=1,2,3,…当a1≥3时,证明对所有的n≥1,有(1)an≥n
设数列{an}满足a1+2a2+3a3+.+nan=n(n+1)(n+2)
数列an满足a1+2a2+3a3+...+nan=(n+1)(n+2) 求通项an
已知数列{an}满足:a1+2a2+3a3+...+nan=(2n-1)*3^n(n属于正整数)求数列{an}得通项公式
对任意正整数n,数列an均满足a1+2a2+3a3+……+nan=n(n+1)(n+2)
已知数列{an}满足a1+a2+a3+…+nan=n(n+1)(n+2),则{an}的通项公式为an=
问道数列题.设数列an满足a1+2a2+3a3+...+nan=2^n(n属于正自然数),则数列an的通项是?
已知数列{an}满足a1+2a2+3a3+…+nan=n(n+1)(n+2),则a1+a2+a3+…+an=多少?
设数列an满足a1=1/2,2nan+1=(n+1)an,求数列an的通项公式
数列An中,a1=3,nAn+1=(n+2)An,求通项an,