急！高中数列问题，好的再加到50，谢谢啦
3个回答
展开全部
(1) 2log(2)a2=log(2)a1+log(2)a3
2log(2)a2=log(2)2+log(2)8
2log(2)a2=1+3=4
log(2)a2=2
a2=4
d=log(2)a2-log(2)a1=log(2)4-log(2)2=1
log(2)an=log(2)a1+d(n-1)=log(2)2+n-1=n
an=2^n
(2) 1/(a(n+1)-an)=1/(2^(n+1)-2^n)=0.5^n
1/(a2-a1)+1/(a3-a2)+……+1/(a(n+1)-an)=0.5+0.5^2+……+0.5^n=1-0.5^n<1
(3) 1/an=0.5^n
Sn=1-0.5^n
nSn=n-n*0.5^n
Tn=n(n+1)/2-(0.5+0.5-0.5^n-n*0.5^(n+1))
=0.5n^2+0.5n-1+0.5^n+n*0.5^(n+1)
2log(2)a2=log(2)2+log(2)8
2log(2)a2=1+3=4
log(2)a2=2
a2=4
d=log(2)a2-log(2)a1=log(2)4-log(2)2=1
log(2)an=log(2)a1+d(n-1)=log(2)2+n-1=n
an=2^n
(2) 1/(a(n+1)-an)=1/(2^(n+1)-2^n)=0.5^n
1/(a2-a1)+1/(a3-a2)+……+1/(a(n+1)-an)=0.5+0.5^2+……+0.5^n=1-0.5^n<1
(3) 1/an=0.5^n
Sn=1-0.5^n
nSn=n-n*0.5^n
Tn=n(n+1)/2-(0.5+0.5-0.5^n-n*0.5^(n+1))
=0.5n^2+0.5n-1+0.5^n+n*0.5^(n+1)
本回答由提问者推荐
已赞过
已踩过<
评论
收起
你对这个回答的评价是？
推荐律师服务：
若未解决您的问题，请您详细描述您的问题，通过百度律临进行免费专业咨询
