Chapter 10: Problem 48
Explicit formulas for sequences Consider the formulas for the following sequences \(\left\\{a_{n}\right\\}_{n=1}^{\infty}\) Make a table with at least ten terms and determine a plausible limit of the sequence or state that the sequence diverges. $$a_{n}=\frac{100 n-1}{10 n}$$
Short Answer
Expert verified
Answer: The sequence converges, and its limit is 10.
Step by step solution
01
Find the first 10 terms of the sequence
Given the formula \(a_n = \frac{100n - 1}{10n}\), we can generate the first ten terms of the sequence by plugging in the values of \(n = 1, 2, 3, ..., 10\).
02
Create a table
Organize these terms in a table to display them clearly. The first column will contain the values of 'n', and the second column will contain the corresponding values of 'a_n'.
| n | \(a_n\) |
|---|-----------------------|
| 1 | \(\frac{99}{10}\) |
| 2 | \(\frac{199}{20}\) |
| 3 | \(\frac{299}{30}\) |
| 4 | \(\frac{399}{40}\) |
| 5 | \(\frac{499}{50}\) |
| 6 | \(\frac{599}{60}\) |
| 7 | \(\frac{699}{70}\) |
| 8 | \(\frac{799}{80}\) |
| 9 | \(\frac{899}{90}\) |
| 10| \(\frac{999}{100}\) |
03
Analyze the sequence
To determine the limit of the given sequence, we should analyze the terms and observe their behavior as 'n' approaches infinity. The formula can be simplified as:
$$a_n = \frac{100n - 1}{10n} = \frac{100 - \frac{1}{n}}{10} = 10 - \frac{1}{10n}$$
04
Determine whether the sequence converges or diverges
Now as 'n' approaches infinity, the denominator of the second term (\(\frac{1}{10n}\)) also increases indefinitely. This causes the second term to approach 0. Consequently, the entire sequence approaches:
$$\lim_{n \to \infty}a_n = 10 - 0 = 10$$
So, the limit of the sequence exists and is equal to 10. Therefore, the sequence converges, and its limit is 10.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Sequence Limits
To understand sequence limits, imagine a sequence like a set of stairs that you're climbing without end. Each step you take is a term in that sequence. A limit of a sequence is a value that the terms of the sequence get closer and closer to as you keep going further up the steps. If a sequence has a limit, it means that as you choose larger and larger numbers from our sequence, the result becomes very close to a single value.
For example, with the given sequence formula \(a_n = \frac{100n - 1}{10n}\), as you plug in larger values of \(n\), the sequence terms approach the number 10. This means the sequence has a limit, which is 10. It's important in mathematics as it helps determine the behavior of sequences as they extend towards infinity.
For example, with the given sequence formula \(a_n = \frac{100n - 1}{10n}\), as you plug in larger values of \(n\), the sequence terms approach the number 10. This means the sequence has a limit, which is 10. It's important in mathematics as it helps determine the behavior of sequences as they extend towards infinity.
Convergence
When we talk about convergence, we're referring to a sequence that draws nearer to a specific value as the sequence progresses. You can think of it as a destination you are aiming for. A sequence is said to converge when it has a limit. In the exercise, as \(n\) becomes very large, \(a_n\) becomes close to 10.
This process means that our sequence converges to 10.
This process means that our sequence converges to 10.
- All the terms are heading towards the same destination.
- The closer \(n\) gets to infinity, the closer the terms of the sequence are to the number 10.
Divergence
Divergence is the opposite of convergence. If a sequence doesn't settle down to a single value, we say it diverges. It can mean either racing towards infinity, or continually bouncing around without getting closer to a particular number.
In our case, \(a_n = \frac{100n - 1}{10n}\) doesn't diverge because as \(n\) increases, \(a_n\) consistently approaches the limit of 10 rather than veering off unpredictably or heading to infinity.
Divergence indicates a lack of a single approaching value and often denotes a more chaotic or unbounded sequence behavior.
In our case, \(a_n = \frac{100n - 1}{10n}\) doesn't diverge because as \(n\) increases, \(a_n\) consistently approaches the limit of 10 rather than veering off unpredictably or heading to infinity.
Divergence indicates a lack of a single approaching value and often denotes a more chaotic or unbounded sequence behavior.
Terminology in Sequences
Understanding the terminology in sequences can greatly simplify your study of these mathematical concepts. Here are a few terms you should get familiar with:
- Term: Each number in the sequence, like a step on a staircase.
- Explicit Formula: A clear formula to find any term in the sequence, like \(a_n = \frac{100n - 1}{10n}\), allows us to plug in a number for \(n\) to get the \(n\)-th term directly.
- Limit: The value that a sequence gets closer to as the numbers in the sequence get larger.
- Convergence/Divergence: Whether a sequence is becoming more like a stable single number or not.