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Question

The series represented by $a_n = \frac{n^2-2n}{3n^2+ n}$ is

The correct answer is
convergent

Identifying Sequence Convergence

A sequence $\{a_n\}$ is considered convergent if its terms approach a specific finite value as $n$ becomes infinitely large. This value is known as the limit of the sequence.

Calculating the Limit of $a_n$

To determine if the sequence defined by $a_n = \frac{n^2-2n}{3n^2+ n}$ converges, we calculate its limit as $n \to \infty$.

  1. Divide the numerator and the denominator by the highest power of $n$ in the denominator, which is $n^2$: $a_n = \frac{\frac{n^2}{n^2}-\frac{2n}{n^2}}{\frac{3n^2}{n^2}+ \frac{n}{n^2}}$ $a_n = \frac{1-\frac{2}{n}}{3+\frac{1}{n}}$
  2. Take the limit as $n \to \infty$. Since $\lim_{n \to \infty} \frac{k}{n} = 0$ for any constant $k$: $\lim_{n \to \infty} a_n = \lim_{n \to \infty} \frac{1-\frac{2}{n}}{3+\frac{1}{n}} = \frac{1-0}{3+0}$ $\lim_{n \to \infty} a_n = \frac{1}{3}$

Conclusion on Convergence

The limit of the sequence $a_n$ as $n$ approaches infinity is $\frac{1}{3}$. Since this limit is a finite value, the sequence $\{a_n\}$ is convergent.

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Important Questions from Infinite Series

  1. Consider the following two series
    P: $\sum_{n=1}^{\infty} \frac{1}{n}$
    Q: $\sum_{n=1}^{\infty} \frac{1}{n^2}$
    Choose the correct option from the following

  2. Consider the following infinite series: 

    $1+r+r^2 + r^3 + ............$ If 

    $r = 0.3$, then the sum of this infinite series is ________

  3. The series $s = \sum_{m=1}^{\infty} \frac{m^2}{3^m} (x - 2)^m$ converges for all $x$ with $|x-2| \le R$ given by
  4. Which one of the following series is divergent?
  5. The value of the series $1+ \sin x + \cos^2 x + \sin^3 x + \dots$ at $x = \frac{ \pi}{4}$ is __________.

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