Limit of the sequence $\lim_{n\to\infty}\left(\frac{\log(n+2)}{\log (n+1)}\right)^{n\log n}$
I want to find the limit of the following sequence
$$x_n=\left(\frac{\log(n+2)}{\log (n+1)}\right)^{n\log n}$$
Try using the logarithmic equivalence criterion, that is:
$$\lim_{n\to\infty}{x_n}^{y_n}=e^L\leftrightarrow \lim_{n\to\infty}{y_n({x_n-1})}=L$$
With the above, try to find the limit of $n\log n\left(\frac{\log(n+2)}{\log (n+1)}-1\right)$
However, I was unsuccessful. Any help regarding this? thank you very much.
The logarithmic equivalence criterion which you are referring seems not necessary, let use instead
$$\left(\frac{\log(n+2)}{\log (n+1)}\right)^{n\log n}=e^{n \log n\log\left(\frac{\log(n+2)}{\log (n+1)}\right)}$$
and by
$$\frac{\log(n+2)}{\log (n+1)} =1+\frac{\log\frac{n+2}{n+1}}{\log (n+1)}$$
we have
$$n \log n\log\left(\frac{\log(n+2)}{\log (n+1)}\right)=\frac{\log\left(1+\frac{\log\frac{n+2}{n+1}}{\log (n+1)}\right)}{\frac{\log\frac{n+2}{n+1}}{\log (n+1)}}\frac{n \log n\log\frac{n+2}{n+1}}{\log (n+1)}$$
with
$$\frac{\log\left(1+\frac{\log\frac{n+2}{n+1}}{\log (n+1)}\right)}{\frac{\log\frac{n+2}{n+1}}{\log (n+1)}}\to 1$$
and
$$\frac{n \log n\log\frac{n+2}{n+1}}{\log (n+1)}=\frac{\log n}{\log (n+1)}\log\left(1+\frac 1{n+1}\right)^n \to 1\cdot \log e =1$$
then
$$\left(\frac{\log(n+2)}{\log (n+1)}\right)^{n\log n}=e^{n \log n\log\left(\frac{\log(n+2)}{\log (n+1)}\right)} \to e^1=e$$
Edit
Using the criterion you are referring to, in the same way as in the previous conclusion, we obtain
$$n\log n\left(\frac{\log(n+2)}{\log (n+1)}-1\right)=n\log n\frac{\log \frac{n+2}{n+1}}{\log (n+1)}\to 1$$