Chapter 2: Problem 7
Calculate, to four decimal places, the first ten terms of the sequence and use them to plot the graph of the sequence. Does the sequence appear to have a limit? If so, calculate it. If not, explain why. \(a_{n}=3+\left(-\frac{2}{3}\right)^{n}\)
Short Answer
Expert verified
The sequence approaches a limit of 3 as \(n\) increases.
Step by step solution
01
Calculate the First Term
To find the first term of the sequence, substitute \( n = 1 \) into the formula. \[a_1 = 3 + \left(-\frac{2}{3}\right)^1 = 3 - \frac{2}{3} = \frac{7}{3} = 2.3333\ (to\ four\ decimal\ places)\]
02
Calculate Subsequent Terms
To get the next terms of the sequence, continue substituting \( n = 2, 3, \ldots, 10 \) into the formula. For instance:1. \( a_2 = 3 + \left(-\frac{2}{3}\right)^2 = 3 + \frac{4}{9} = \frac{31}{9} = 3.4444\)2. \( a_3 = 3 + \left(-\frac{2}{3}\right)^3 = 3 - \frac{8}{27} = \frac{73}{27} = 2.7037\)3. Continue this pattern up to \( a_{10} \).
03
List All Ten Terms
The first ten terms calculated to four decimal places are:\[a_1 = 2.3333, \ a_2 = 3.4444, \ a_3 = 2.7037, \a_4 = 3.2963, \ a_5 = 2.8025, \ a_6 = 3.1975, \a_7 = 2.8678, \ a_8 = 3.1321, \ a_9 = 2.9119, \ a_{10} = 3.0881 \].
04
Plot the Sequence
Plot the points \((n, a_n)\) on a graph where the x-axis represents the term number \(n\) and the y-axis represents the term value \(a_n\). You'll notice the terms oscillate closer and closer around 3.
05
Determine the Limit of the Sequence
Observe the plot and the values of the terms calculated. As \( n \) increases, the contribution of \( \left(-\frac{2}{3}\right)^n \) becomes smaller, and \(a_n\) approaches 3. Therefore, the sequence has a limit of 3 as \(n\) approaches infinity.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Sequence Terms
In any sequence, each term represents an individual element defined by a specific formula or rule related to its position within the sequence. Here, the formula given is \ \(a_{n}=3+\left(-\frac{2}{3}\right)^{n}\ \). This formula helps to determine the value of each sequence term based on the term's position, \(n\). For example, by substituting \(n = 1\), we calculate the first term as \(a_1 = 2.3333\), and by substituting \(n = 2\), we find the second term to be \(a_2 = 3.4444\).
In the provided solution, the terms are developed step-by-step:
In the provided solution, the terms are developed step-by-step:
- Substitute different values of \(n\) (from 1 to 10) into the formula.
- Each substitution reveals the exact value of the sequence term at that position.
- The result is a detailed listing of the sequence terms like \(a_1 = 2.3333\), \(a_2 = 3.4444\), and so forth.
Sequence Graph
A sequence graph is a visual representation of a sequence, typically plotted on a two-dimensional coordinate system. It pairs each sequence term with its position in the sequence. In our exercise, the sequence terms \((a_n)\) are plotted against their respective positions \((n)\), with \(n\) on the x-axis and \(a_n\) on the y-axis.
Creating the graph involves these steps:
Creating the graph involves these steps:
- Identify the range of terms to be plotted. Here, terms from \(n = 1\) to \(n = 10\) are used.
- Plot each term: for instance, \((1, 2.3333)\), \((2, 3.4444)\), etc.
- Connect these points to observe any noticeable pattern or behavior.
Recursive Sequence
A recursive sequence is one where subsequent terms are determined based on previous terms using a specific rule. Although not explicitly recursive, sequences like \(a_{n}=3+\left(-\frac{2}{3}\right)^{n}\) share a somewhat similar trait where terms change systematically based on an established definition. Let's consider aspects of recursive sequences to link with our sequence.
Key elements include:
Key elements include:
- Base case: Initial terms are usually defined to start the sequence.
- Recursive rule: Uses previous term(s) to generate the next. Although not in this formula, note that the change factor \(-\frac{2}{3}\) affects successive terms.
Sequence Analysis
Sequence analysis involves studying the behavior of sequence terms over time, including any pattern, convergence, or limit. For a sequence like \ \(a_{n}=3+\left(-\frac{2}{3}\right)^{n}\ \), sequence analysis enables students to predict long-term outcomes and understand the sequence's tendency.
The process includes:
The process includes:
- Identifying initial value and pattern: Knowing that the sequence starts with \(a_1 = 2.3333\), students observe how each subsequent term varies.
- Examining oscillations and convergence: Each term fluctuates alternately above and below the central value of 3, revealing a converging pattern.
- Determining the limit: The terms closing toward 3 instructs the analyst that the sequence’s limit is 3 as \(n\) becomes very large.