Math Problem Statement

convergence of sequence -1^n/n

Solution

The sequence in question is an=(1)nna_n = \frac{(-1)^n}{n}. We want to determine whether this sequence converges, and if it does, find the limit.

Step-by-Step Analysis:

  1. General Term: The sequence is given by: an=(1)nna_n = \frac{(-1)^n}{n} Here, (1)n(-1)^n alternates between 1-1 and 11 depending on whether nn is odd or even, respectively.

  2. Behavior of the Sequence:

    • When nn is even: an=1na_n = \frac{1}{n}
    • When nn is odd: an=1na_n = \frac{-1}{n}

    As nn increases, the absolute value of ana_n decreases because 1n\frac{1}{n} tends to zero.

  3. Convergence:

    • To determine the limit of ana_n as nn approaches infinity, observe that: limn1n=0andlimn1n=0\lim_{n \to \infty} \frac{1}{n} = 0 \quad \text{and} \quad \lim_{n \to \infty} \frac{-1}{n} = 0
    • Since both 1n\frac{1}{n} and 1n\frac{-1}{n} tend to 0 as nn becomes large, regardless of whether nn is odd or even, the entire sequence tends to 0.
  4. Conclusion: The sequence converges to 0. In other words: limnan=0\lim_{n \to \infty} a_n = 0

Summary:

The sequence an=(1)nna_n = \frac{(-1)^n}{n} converges, and its limit is 00.

Would you like more details or have any questions?


Related Questions:

  1. What is the difference between pointwise convergence and uniform convergence?
  2. How can we determine if a series converges using the comparison test?
  3. What is the difference between absolute convergence and conditional convergence?
  4. How do we prove that a sequence is bounded?
  5. What is the Cauchy criterion for convergence of a sequence?
  6. How does the squeeze theorem help in determining the limit of a sequence?
  7. What is the relationship between convergence of a sequence and the convergence of its corresponding series?
  8. How does the Alternating Series Test determine the convergence of a series?

Tip: When analyzing sequences, it’s important to consider both the behavior as nn increases and the nature of any alternating terms.

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Math Problem Analysis

Mathematical Concepts

Sequences
Convergence

Formulas

Limit of a sequence

Theorems

Limit properties

Suitable Grade Level

Advanced Undergraduate