Chapter 1: Problem 20
20\. $$a_{1}=3, a_{n+1}=\sqrt{3 a_{n}}$$
Short Answer
Expert verified
Every term in the sequence is 3; \(a_n = 3\) for all \(n\).
Step by step solution
01
Understand the Sequence
We are dealing with a recursively defined sequence where the first term \(a_1 = 3\) and each subsequent term is defined by \(a_{n+1} = \sqrt{3 a_n}\). This means to find \(a_2\), \(a_3\), and so on, we will use the last found term and calculate the next one using this formula.
02
Calculate the Second Term
Substitute \(n = 1\) into the recursive formula to find \(a_2\): \[a_2 = \sqrt{3a_1} = \sqrt{3 \times 3} = \sqrt{9} = 3.\] Thus, \(a_2 = 3\).
03
Calculate the Third Term
Similarly, substitute \(n = 2\) into the recursive formula to find \(a_3\): \[a_3 = \sqrt{3a_2} = \sqrt{3 \times 3} = \sqrt{9} = 3.\] Thus, \(a_3 = 3\).
04
General Observations for the Sequence
From steps 2 and 3, we can observe that \(a_2\) and \(a_3\) are both 3, just like \(a_1\). As actually verified by calculation, it appears each term \(a_n\) equals 3, suggesting \(a_{n+1} = 3\). Therefore, by the recursion given, all terms in the sequence are equal to 3.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Calculus for Life Sciences
Calculus is a fundamental aspect of life sciences, offering tools to model and analyze biological phenomena. In the life sciences, calculus helps in understanding growth models, population dynamics, and much more. Consider a situation where you're observing a population whose size changes over time, similar to a sequence.
- Population Growth: Calculus can aid in analyzing how a population evolves by modeling it with sequences and differential equations.
- Decaying Substances: In the study of medication within the body, calculus comes into play to describe how drugs decrease in concentration over time.
- Temperature Fluctuations: Calculating how an organism's internal temperature responds to external variations can involve sequences and series.
Sequence Recursion
Sequence recursion is a fascinating concept in mathematics, allowing us to define sequences with a rule that relates each term to previous ones. Unlike sequences defined outright, recursive sequences build gradually.In our exercise, we have a recursive sequence starting with a base of 3, and each subsequent term depends on the previous one through the formula:
\(a_{n+1} = \sqrt{3a_n}\).
\(a_{n+1} = \sqrt{3a_n}\).
- Defining the Base: Every recursive sequence begins with an initial term, here \(a_1 = 3\). This starting point is crucial as it dictates subsequent values.
- Recursive Formula: The rule applied to get from one term to the next,
guides the formation of the sequence. It's a function of the preceding terms. - Structure of the Sequence: The repeated application of the formula results in an interesting pattern.
For this sequence, every term remains constant at 3.
Mathematical Induction
Mathematical induction is a powerful tool, mainly used to prove that a statement is true for every natural number. The concept is akin to falling dominoes; if you push the first, the rest will follow.
- Base Case: Induction starts by proving the validity of a statement for an initial case, often involving the smallest number.
- Inductive Step: The next part is assuming the statement holds for an arbitrary number \(n\).
Then you show it must also work for \(n+1\), confirming a crucial chain of logic.