等比数列{an}为2的(n-1)次方,bn=2(log2(an)+1)(n是正整数).
证明,不等式[(b1+1)/b1]*……[(bn+1)/bn]>根号(n+1)
人气:435 ℃ 时间:2019-08-26 07:44:46
解答
因为an=2^(n-1),所以bn=2(log2(an)+1)=2[((n-1)+1]=2n,所以(bn+1)/bn=(2n+1)/2n,又因为(2n+1)^2=4n^2+4n+1>4n^2+4n=4n(n+1),所以(2n+1)^2/4n^2>(n+1)/n,(2n+1)/2n>√(n+1)/√n.所以[(b1+1)/b1]*……[(bn+1)/bn=3/2*5...
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