Math Problem Statement

what test would you use here

what test would you use here

Solution

To determine the convergence or divergence of the series

n=2nln(n),\sum_{n=2}^{\infty} \frac{n}{\ln(n)},

we can apply the Comparison Test or the Integral Test, as these are useful for series involving terms with logarithmic functions.

Reasoning for Test Selection:

  1. Comparison Test: We can compare nln(n)\frac{n}{\ln(n)} with a known divergent series, as it resembles a harmonic-like series (which tends to diverge). We know that 1n\sum \frac{1}{n} diverges, and nln(n)\frac{n}{\ln(n)} grows even faster than 1n\frac{1}{n}, suggesting divergence.

  2. Integral Test: By converting the sum into an integral, xln(x)dx\int \frac{x}{\ln(x)} dx, and examining whether this integral converges or diverges, we can determine the behavior of the series.

For this specific case, the Integral Test would be quite suitable because we can analyze the integral:

2xln(x)dx.\int_{2}^{\infty} \frac{x}{\ln(x)} \, dx.

This integral diverges, implying that the series n=2nln(n)\sum_{n=2}^{\infty} \frac{n}{\ln(n)} also diverges.

Would you like a detailed explanation of the calculations, or do you have further questions?

Related Questions

  1. How does the Comparison Test work for determining convergence or divergence?
  2. Can the Ratio Test be applied to this series, and if so, what does it show?
  3. Why does the series 1n\sum \frac{1}{n} diverge?
  4. What other types of series typically use the Integral Test?
  5. How does logarithmic growth affect the convergence of series?

Tip

When dealing with logarithmic terms in series, consider using the Integral Test or Comparison Test with a similar simpler series for quicker insights into convergence behavior.

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Math Problem Analysis

Mathematical Concepts

Infinite Series
Convergence and Divergence
Logarithmic Functions

Formulas

\(\sum_{n=2}^{\infty} \frac{n}{\ln(n)}\)

Theorems

Comparison Test
Integral Test

Suitable Grade Level

Undergraduate Calculus