Why Is the Limit of This $\ln$ Sequence Incorrect?

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SUMMARY

The limit of the sequence defined by \( a_n = \ln\left(\frac{n}{n^2 + 1}\right) \) as \( n \) approaches infinity is incorrectly assumed to be \( -\infty \) by substituting the limit of \( \frac{n}{n^2 + 1} \), which is \( 0 \). The correct approach involves recognizing that \( \frac{n}{n^2 + 1} \) approaches \( 0 \) but does not allow direct substitution into the logarithm. Instead, applying L'Hôpital's Rule or analyzing the behavior of the logarithm as \( n \) increases reveals that the limit converges to \( 0 \), not \( -\infty \).

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If I have this sequence

$$a_n = \ln\left({\frac{n}{n^2 + 1}}\right)$$

I need to find:

$$ \lim_{{n}\to{\infty}} \ln\left({\frac{n}{n^2 + 1}}\right)$$

Shouldn't I be able to find the limit of$$ \lim_{{n}\to{\infty}} \frac{n}{n^2 + 1}$$ (which is $0$) and then substitute the result of that into the original limit and get the answer there?

So if I substitute in 0 I would get

$$ \lim_{{n}\to{\infty}} \ln\left({0}\right)$$

which would be negative $\infty$. However this is the incorrect answer.
 
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Why do you think that the result is incorrect?
 

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