Math Problem Statement
Question 1: Suppose (an) is a sequence defined by an = 1 n+1 for n = 1, 2, 3, . . ..
- Prove that the sequence (an) converges.
- Find the limit of the sequence as n → ∞.
- Explain intuitively why this limit makes sense in terms of the behavior of the sequence’s terms as n increases.
Solution
To address this problem comprehensively, let's tackle each part step by step.
Part 1: Prove that the sequence converges
The sequence is given by: for .
To prove that converges, let's analyze its behavior as becomes very large.
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Monotonicity: Notice that is positive for all and decreases as increases. To confirm this, observe that , and since , it follows that . Therefore, is a decreasing sequence.
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Boundedness: Since is always positive, we know for all . Therefore, is bounded below by .
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Conclusion: By the Monotone Convergence Theorem, any sequence that is both decreasing and bounded below must converge. Therefore, converges.
Part 2: Find the limit of the sequence as
To find the limit, we examine :
As , the term grows indefinitely, causing to approach . Thus, we conclude:
Part 3: Intuitive Explanation of the Limit
Intuitively, as increases, the denominator in the expression becomes larger and larger, making the fraction smaller. This trend indicates that each term in the sequence becomes closer to zero as grows. The limit of zero aligns with this intuition, as the terms of the sequence approach zero in value as they progress, illustrating a common pattern in sequences where the reciprocal of a linearly increasing term leads to a zero limit.
In summary:
- The sequence converges because it is decreasing and bounded below.
- The limit of as is .
- Intuitively, this makes sense because the terms get smaller as increases due to the growing denominator.
Would you like further clarification on any of these steps?
Here are five related questions that might help deepen your understanding:
- Can you prove convergence for other types of sequences, such as ?
- How does the limit of a sequence differ from a limit of a function as ?
- What happens if you alter the sequence definition to ?
- Why is the Monotone Convergence Theorem helpful for proving convergence?
- How do we approach convergence proofs for non-monotonic sequences?
Tip: In many cases, you can determine a sequence's limit by examining how its formula behaves as approaches infinity.
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Math Problem Analysis
Mathematical Concepts
Sequences and Series
Limits
Convergence of Sequences
Formulas
Limit of sequence formula: lim(n→∞) an
Theorems
Monotone Convergence Theorem
Suitable Grade Level
Undergraduate