Chapter 9: Problem 18
Do the sequences, converge or diverge? If a sequence converges, find its limit. $$\frac{2^{n}}{3^{n}}$$
Short Answer
Expert verified
The sequence converges, and its limit is 0.
Step by step solution
01
Understand the Sequence
The given sequence is \( \left( \frac{2^{n}}{3^{n}} \right) \). We need to determine whether this sequence converges or diverges. If it converges, we will find its limit.
02
Simplify the Sequence
Observe that the term \( \frac{2^{n}}{3^{n}} \) can be rewritten as \( \left( \frac{2}{3} \right)^{n} \). This step helps us understand the structure of the sequence.
03
Determine Limit Behavior
Since \( \left( \frac{2}{3} \right) \) is a positive fraction less than one, as \( n \) becomes very large, \( \left( \frac{2}{3} \right)^{n} \) approaches zero. This is because repeatedly multiplying by a number smaller than one results in smaller and smaller values.
04
Conclusion on Convergence
We conclude that the sequence \( \left( \frac{2^{n}}{3^{n}} \right) = \left( \frac{2}{3} \right)^{n} \) converges. The limit of the sequence as \( n \to \infty \) is 0.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
The Limit of a Sequence
When working with sequences, one of the main questions is whether a sequence reaches a specific value as it progresses. This specific value is known as the "limit" of the sequence. For any sequence \(a_n\), if there exists a real number \(L\) such that as \(n\) increases towards infinity, \(a_n\) gets arbitrarily close to \(L\), then \(L\) is called the limit of the sequence.
- If \(a_n\) actually approaches \(L\) in this way, we write \( \lim_{{n \to \infty}} a_n = L \).
- In simple terms, the terms of the sequence "settle down" at \(L\).
Exponential Sequences
Exponential sequences are sequences where each term can be expressed as a constant base raised to an increasing power, typically written as \(a^n\). They exhibit behavior that drastically depends on the base:
- If the base \(a\) is greater than 1, the sequence grows rapidly without bound.
- If the base \(a\) is exactly 1, the sequence remains constant at 1 for all terms.
- If the base \(a\) is between 0 and 1, the sequence shrinks and heads towards zero as \(n\) increases.
- If the base \(a\) is negative, the sequence will oscillate, making its behavior more complex.
Convergence and Divergence
In the study of sequences, determining whether a sequence converges or diverges is crucial. Convergence means that the terms of the sequence are getting closer together around a certain value, while divergence means they are not settling at any particular value.
To determine if a sequence converges or diverges:
To determine if a sequence converges or diverges:
- Examine if the sequence's terms approach a fixed number as the sequence progresses. If they do, it converges.
- If the terms keep increasing or decreasing without approaching a specific number, or if they oscillate indefinitely, the sequence diverges.