Skip to main content
Ch. 10 - Infinite Sequences and Series
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
Chapter 10, Problem 10.1.36

Convergence and Divergence
Which of the sequences {aₙ} in Exercises 31–100 converge, and which diverge? Find the limit of each convergent sequence.
aₙ = (n + 3) / (n² + 5n + 6)

Verified step by step guidance
1
Identify the given sequence: \(a_n = \frac{n + 3}{n^2 + 5n + 6}\).
To analyze convergence or divergence, examine the behavior of \(a_n\) as \(n\) approaches infinity, i.e., find \(\lim_{n \to \infty} a_n\).
Since the sequence is a rational function of \(n\), compare the degrees of the numerator and denominator polynomials. The numerator is degree 1, and the denominator is degree 2.
Divide both numerator and denominator by the highest power of \(n\) in the denominator, which is \(n^2\), to simplify the limit expression: \(a_n = \frac{\frac{n}{n^2} + \frac{3}{n^2}}{\frac{n^2}{n^2} + \frac{5n}{n^2} + \frac{6}{n^2}} = \frac{\frac{1}{n} + \frac{3}{n^2}}{1 + \frac{5}{n} + \frac{6}{n^2}}\).
Evaluate the limit by letting \(n\) approach infinity, noting that terms with \(\frac{1}{n}\) and \(\frac{1}{n^2}\) approach zero, and conclude whether the sequence converges or diverges based on this limit.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
2m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Sequence Convergence and Divergence

A sequence converges if its terms approach a specific finite value as n approaches infinity; otherwise, it diverges. Understanding this helps determine the behavior of {aₙ} as n grows large.
Recommended video:
Guided course
8:22
Introduction to Sequences

Limits of Sequences

The limit of a sequence is the value that the terms get arbitrarily close to as n becomes very large. Calculating limits often involves simplifying expressions and applying limit laws.
Recommended video:
Guided course
8:22
Introduction to Sequences

Asymptotic Behavior of Rational Functions

For sequences defined by rational functions like (n + 3)/(n² + 5n + 6), analyzing the degrees of numerator and denominator polynomials helps determine the limit, since higher-degree denominators typically drive the sequence to zero.
Recommended video:
5:50
Asymptotes of Hyperbolas