an=3*2^(n-1)/((2^n+1)(2^n-1))证明:1/a1+1/a2+1/a3+……1/an抱歉,是1/an=3*2^(n-1)/((2^n+1)(2^n-1))
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an=3*2^(n-1)/((2^n+1)(2^n-1))证明:1/a1+1/a2+1/a3+……1/an抱歉,是1/an=3*2^(n-1)/((2^n+1)(2^n-1))an=3*2^(n-1)
an=3*2^(n-1)/((2^n+1)(2^n-1))证明:1/a1+1/a2+1/a3+……1/an抱歉,是1/an=3*2^(n-1)/((2^n+1)(2^n-1))
an=3*2^(n-1)/((2^n+1)(2^n-1))
证明:1/a1+1/a2+1/a3+……1/an
抱歉,是1/an=3*2^(n-1)/((2^n+1)(2^n-1))
an=3*2^(n-1)/((2^n+1)(2^n-1))证明:1/a1+1/a2+1/a3+……1/an抱歉,是1/an=3*2^(n-1)/((2^n+1)(2^n-1))
应该是1/an=3*2^(n-1)/((2^n+1)(2^n-1))吧,否则结论不成立啊.按这个做,还行.
a1=1,易证n>=2时,3*2^(n-1)/((2^n+1)(2^n-1))=3*2^(n-1)/(4^n)-1
题目肯定是写错了。
经判断知an恒>0
a1=3·1/[(2+1)(2-1)]=1 1/a1=1/1=1
a2=3·2/[(4+1)(4-1)]=6/15=2/5 1/a2=5/2
1/a1+1/a2=1+ 5/2=7/2>2,仅仅前两项和已经>2了。
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