[Math] Limit comparison Test for series 1/(n^2 * log n ) converge or diverge

limits

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Doubt – used inequality, $1/(n^2 \log n) < 1/ n^2$ will be true only for $n > 10$ as $\log n < 1$ for $1 < n < 10 $. but here summation is running from $n= 2$ to infinite
please check whether the solution which is arrived is correct with the correct procedure.

Best Answer

Your idea is right, we have that

$$\frac{\frac1{n^2 \log n}}{\frac1{n^2}}=\frac1{\log n} \to 0$$

and therefore by LCT the given series converges.

Note that the initial values are not relevant here since we are interested to the behaviour for $n$ larg and also the inequality $1/(n^2 \log n) < 1/ n^2$ is not an issue when we use LCT.

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