Question

Determine whether the following series converges or diverges using any test. Be sure to clearly state what test(s) you are using and check any conditions needed to apply that test.

Answer 1

According to the ratio criterion, the rational series presented in the picture converges as x < 1. The limit L was 4 /5.

How to determine whether a series converges by ratio criterio

Herein we have a series in rational form, whose convergence can be proved by the ratio criterion, whose defintion is shown below:

x = lim (n → ∞) |aₙ/aₙ₊₁|   (1)

The series converges if x < 0 and diverges when x > 1. If x = 1, the criterion cannot be used and another criterion must be used instead. Now we proceed to apply it on the expression behind the series:

|aₙ/aₙ₊₁| = [(2 · n + 1) · (2 · n + 2)] / [5 · (n + 1)²]

|aₙ/aₙ₊₁| = [4 · n² + 5 · n + 2] / [5 · n² + 10 · n + 5]

Then, by applying the limit property for rational equations we find that limit of the expression within the series is:

L = 4 / 5

According to the ratio criterion, the rational series presented in the picture converges as x < 1. The limit L was 4 /5.

To learn more on convergent series: https://brainly.com/question/15415793

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Answer 2

By the ratio test, the series diverges.

$\displaystyle \lim_{k\to\infty} \left| \frac{5^{k+1} ((k+1)!)^2}{(2(k+1))!} \cdot \frac{(2k)!}{(5^k (k!)^2}\right| = 5 \lim_{k\to\infty} \frac{(k+1)^2}{(2k+2)(2k+1)} = \frac54 > 1$