Chapter 9: Problem 29
Find the general term of the sequence, starting with \(n=1,\) determine whether the sequence converges, and if so find its limit. $$(\sqrt{2}-\sqrt{3}),(\sqrt{3}-\sqrt{4}),(\sqrt{4}-\sqrt{5}), \ldots$$
Short Answer
Expert verified
The sequence converges to 0.
Step by step solution
01
Identify the Pattern of the Sequence
The given sequence is \((\sqrt{2}-\sqrt{3}), (\sqrt{3}-\sqrt{4}), (\sqrt{4}-\sqrt{5}), \ldots\). We can see a pattern here where each term in the sequence has the form \(a_n = \sqrt{n+1} - \sqrt{n+2}\).
02
Find the General Term
Based on the observed pattern, we conjecture that the general term of the sequence is \(a_n = \sqrt{n+1} - \sqrt{n+2}\) for \(n\geq 1\).
03
Determine Convergence
To find if the sequence converges, we need to find \(\lim_{n \to \infty} a_n\). We have \(a_n = \sqrt{n+1} - \sqrt{n+2}\).
04
Simplify the Limit Expression
By rationalizing the expression, compute:\[ \lim_{n \to \infty} a_n = \lim_{n \to \infty} (\sqrt{n+1} - \sqrt{n+2}) \cdot \frac{\sqrt{n+1} + \sqrt{n+2}}{\sqrt{n+1} + \sqrt{n+2}} \]This yields:\[ \lim_{n \to \infty} \frac{(n+1) - (n+2)}{\sqrt{n+1} + \sqrt{n+2}} = \lim_{n \to \infty} \frac{-1}{\sqrt{n+1} + \sqrt{n+2}} \]
05
Evaluate the Limit
The expression becomes:\[\lim_{n \to \infty} \frac{-1}{\sqrt{n+1} + \sqrt{n+2}}\]As \(n\) approaches infinity, both \(\sqrt{n+1}\) and \(\sqrt{n+2}\) approach infinity. Thus:\[\lim_{n \to \infty} \frac{-1}{\sqrt{n+1} + \sqrt{n+2}} = 0\]
06
Conclusion
Since the limit of the sequence \(a_n\) as \(n\) approaches infinity is 0, the sequence converges, and its limit is 0.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Convergence of Sequences
When we talk about the convergence of a sequence, we are referring to whether or not the sequence approaches a particular value as we progress along it, getting closer and closer to that value without ever actually departing from it. A converging sequence has terms that become arbitrarily close to a specific numerical value called the limit as the sequence progresses. In the sequence given in the exercise, the general form of each term is \[a_n = \sqrt{n+1} - \sqrt{n+2}\], showing that as the sequence progresses by increasing \(n\), we eventually determine if the terms are moving towards some stable value. To see if a sequence converges, we evaluate its behavior as \(n\) approaches infinity. This involves analyzing whether the difference between consecutive terms diminishes and gets closer to zero with larger values of \(n\).
- If the values in the sequence approach a finite number, the sequence is said to converge.
- If the sequence does not settle towards a single value, it's called divergent.
Limit of a Sequence
The limit of a sequence is a critical concept when analyzing its behavior at infinity. For a sequence \(a_n\), the limit is the value that the terms \(a_n\) approach as \(n\) becomes indefinitely large. If the terms of the sequence get closer and closer to a specific number, this constitutes a limit. In mathematical terms, we write the limit of a sequence \(a_n\) as \(n\) approaches infinity as: \[\lim_{n \to \infty} a_n\]In our particular sequence, which follows \(a_n = \sqrt{n+1} - \sqrt{n+2}\), we see as \(n\) increases, both \(\sqrt{n+1}\) and \(\sqrt{n+2}\) grow towards infinity, making their difference, \(a_n\), diminish and approach zero. This resulting limit of 0 signifies that the sequence converges to zero. Generally:
- Finding the limit of a sequence provides insight into the long-term behavior of the sequence.
- When the limit exists, it can offer valuable information about stability or other characteristics of the system modeled by the sequence.
General Term of a Sequence
The general term of a sequence is the expression that defines each term of the sequence in relation to its position. This term acts as a formula, allowing us to compute any term of the sequence directly, without listing all prior terms. Knowing the general term is useful because it provides a mathematical representation for any term \(a_n\) based on its index \(n\). In the problem at hand, the sequence follows a specific pattern. By careful observation, we deduced that each term can be expressed as: \[a_n = \sqrt{n+1} - \sqrt{n+2}\]. This expression serves as the **general term** of our sequence.
- Having a general term enables us to swiftly identify any term in the sequence without exhaustive computation.
- It helps in determining properties like convergence, limits, or even the sum if the sequence were a part of a series.