设n∈N,n>1.求证:logn (n+1)>log(n+1) (n+2)

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设n∈N,n>1.求证:logn (n+1)>log(n+1) (n+2)
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设n∈N,n>1.求证:logn (n+1)>log(n+1) (n+2)
设n∈N,n>1.求证:logn (n+1)>log(n+1) (n+2)

设n∈N,n>1.求证:logn (n+1)>log(n+1) (n+2)
证明 要证明 logn (n+1)>log(n+1) (n+2) n∈N,n>1.
系需要证 logn(n+1)/log(n+1)(n+2)>1 即可
logn(n+1)/log(n+1)(n+2)
=[lg(n+1)/lgn]/[lg(n+1)/lg(n+2)]
=lg(n+2)/lgn
>1
所以 logn (n+1)>log(n+1) (n+2) 成立.