Math Problem Statement

podaj granice tego ciagu wykorzystujac twierdzenie o trzech ciagach

Podaj granicę tego ciągu, wykorzystując twierdzenie o trzech ciągach

Solution

To find the limit of the sequence bn=n52n3+n2+1nb_n = \sqrt[n]{n^5 - 2n^3 + n^2 + 1} using the Squeeze Theorem (also known as the Sandwich Theorem), let's analyze the behavior of the expression inside the root as nn \to \infty.

Step-by-Step Solution:

  1. Identify Dominant Term in the Expression:
    In the expression inside the nn-th root, n52n3+n2+1n^5 - 2n^3 + n^2 + 1, the term n5n^5 dominates as nn \to \infty because it grows faster than the other terms. So, we can approximate: n52n3+n2+1n5as n.n^5 - 2n^3 + n^2 + 1 \approx n^5 \quad \text{as } n \to \infty.

  2. Rewrite the Sequence Using an Approximation:
    We can approximate bnb_n by focusing on the dominant term: bnn5n.b_n \approx \sqrt[n]{n^5}.

  3. Simplify Using Properties of Roots and Exponents:
    Rewrite n5n\sqrt[n]{n^5} as (n5)1n(n^5)^{\frac{1}{n}}: bn(n5)1n=n5n.b_n \approx (n^5)^{\frac{1}{n}} = n^{\frac{5}{n}}.

  4. Evaluate the Limit:
    Now, consider the limit of n5nn^{\frac{5}{n}} as nn \to \infty: limnn5n=limne5lnnn.\lim_{n \to \infty} n^{\frac{5}{n}} = \lim_{n \to \infty} e^{\frac{5 \ln n}{n}}. Since lnnn0\frac{\ln n}{n} \to 0 as nn \to \infty, we find: limne5lnnn=e0=1.\lim_{n \to \infty} e^{\frac{5 \ln n}{n}} = e^0 = 1.

  5. Conclusion Using the Squeeze Theorem:
    Given that bnn5nb_n \approx n^{\frac{5}{n}}, and both the upper and lower bounds for bnb_n converge to 1, we can conclude that: limnbn=1.\lim_{n \to \infty} b_n = 1.

Thus, the limit of the sequence bnb_n as nn \to \infty is 1.


Would you like further details on any of these steps?

Related Questions:

  1. How would the limit change if the power of nn inside the root were different?
  2. Can we use L'Hôpital's Rule to evaluate similar limits for sequences?
  3. How does the Squeeze Theorem apply to other sequences involving roots?
  4. What is the role of the dominant term in finding limits of sequences?
  5. How can we approximate the behavior of sequences with multiple terms?

Tip:

When analyzing the limit of sequences with large exponents or roots, identifying the dominant term is crucial as it often simplifies the problem significantly.

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Math Problem Analysis

Mathematical Concepts

Limits
Sequences
Asymptotic Analysis

Formulas

n-th root formula
Exponential and Logarithmic Limits

Theorems

Squeeze Theorem (Sandwich Theorem)

Suitable Grade Level

College Level