Chapter 9: Problem 18
Write the first five terms of the geometric sequence. $$a_{1}=2, r=\pi$$
Short Answer
Expert verified
The first five terms of the geometric sequence are: \(2, 2\pi, 2\pi^2, 2\pi^3, 2\pi^4\).
Step by step solution
01
Compute the Second Term of the Sequence
We use the geometric sequence formula with \(n=2\). Therefore \(a_{2} = a_{1} \cdot r^{(2-1)} = 2 \cdot \(\pi\)^{1} = 2\pi\).
02
Compute the Third Term of the Sequence
By substituting \(n=3\) into the formula, we get \(a_{3} = a_{1} \cdot r^{(3-1)} = 2 \cdot \(\pi\)^{2} = 2\pi^2\).
03
Compute the Fourth Term of the Sequence
Following the same method, we get \(a_{4} = a_{1} \cdot r^{(4-1)} = 2 \cdot \(\pi\)^{3} = 2\pi^3\).
04
Compute the Fifth Term of the Sequence
Finally, for the fifth term, \(a_{5} = a_{1} \cdot r^{(5-1)} = 2 \cdot \(\pi\)^{4} = 2\pi^4\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding a Sequence
When we talk about a sequence in mathematics, we're referring to an ordered list of numbers. Each number in the list is called a term. A sequence can be finite or infinite, depending on whether it has a limited number of terms or continues indefinitely. In the context of a geometric sequence, each term is derived by multiplying the previous term by a fixed non-zero number called the common ratio.
- An example of a sequence could be 2, 4, 8, 16, where each term follows a rule or pattern.
- In a geometric sequence, this rule involves multiplying by a constant.
- The order of the numbers is crucial because it reflects the structure of the sequence.
Grasping the Common Ratio
In a geometric sequence, the common ratio is the factor that each term is multiplied by to yield the next term. It plays a vital role in determining how the sequence progresses. This ratio can be positive, negative, or even a fraction.
- In our example, the common ratio is \(\pi\), which indicates that each term is multiplied by \(\pi\) to get the following term.
- To find any term in the sequence, you multiply the previous term by this common ratio.
- If the common ratio is greater than one, the sequence will grow, while a ratio between zero and one will cause it to shrink.
Exploring Sequence Terms
Each term in a geometric sequence can be calculated using the initial term and the common ratio. The formula for finding any term \(a_n\) in a geometric sequence is:\[ a_n = a_1 \cdot r^{(n-1)} \]Here, \(a_1\) is the first term, \(r\) is the common ratio, and \(n\) is the position of the term in the sequence.
- The first term, \(a_1\), is given directly as part of the sequence.
- To find the second term, you multiply \(a_1\) by \(r\); for the third term, multiply the previous term again by \(r\), and so on.
- An understanding of this process allows for the calculation of any term in the sequence without having to know the previous terms.