Math Problem Statement

Find \( \lim_{n \to \infty} \left( \frac{3n + 3}{n + 2} - \frac{2n + 2}{2n + 4} \right)^2 \)

Solution

The given limit is:

limn(3n+3n+22n+22n+4)2\lim_{n \to \infty} \left( \frac{3n + 3}{n + 2} - \frac{2n + 2}{2n + 4} \right)^2

Let's break this down step by step:

Step 1: Simplify each term inside the parentheses as nn \to \infty.

  • For the first term: 3n+3n+2\frac{3n + 3}{n + 2}, factor out nn from the numerator and the denominator:

3n+3n+2=n(3+3n)n(1+2n)=3+3n1+2n.\frac{3n + 3}{n + 2} = \frac{n(3 + \frac{3}{n})}{n(1 + \frac{2}{n})} = \frac{3 + \frac{3}{n}}{1 + \frac{2}{n}}.

As nn \to \infty, both 3n\frac{3}{n} and 2n\frac{2}{n} tend to zero, so this term tends to 31=3\frac{3}{1} = 3.

  • For the second term: 2n+22n+4\frac{2n + 2}{2n + 4}, factor out nn from the numerator and denominator:

2n+22n+4=n(2+2n)n(2+4n)=2+2n2+4n.\frac{2n + 2}{2n + 4} = \frac{n(2 + \frac{2}{n})}{n(2 + \frac{4}{n})} = \frac{2 + \frac{2}{n}}{2 + \frac{4}{n}}.

As nn \to \infty, both 2n\frac{2}{n} and 4n\frac{4}{n} tend to zero, so this term tends to 22=1\frac{2}{2} = 1.

Step 2: Subtract the two simplified terms.

Now we subtract the two terms:

limn(31)2=(2)2=4.\lim_{n \to \infty} \left( 3 - 1 \right)^2 = (2)^2 = 4.

Final Answer:

The value of the limit is 4\boxed{4}.

Would you like more details on any specific step or have any other questions?

Follow-up Questions:

  1. How would the solution change if the powers inside the limit were different (e.g., cube instead of square)?
  2. What happens if the terms in the denominator grow faster than the numerator as nn \to \infty?
  3. Can L'Hopital's rule be applied to simplify this limit problem?
  4. How do limits at infinity differ from limits at finite points?
  5. What is the significance of factoring out nn when dealing with limits involving large values of nn?

Tip:

When simplifying limits involving infinity, try to factor out the highest power of nn to see the leading behavior of the expression.

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Math Problem Analysis

Mathematical Concepts

Limits
Asymptotic behavior
Simplification of expressions at infinity

Formulas

\( \lim_{n \to \infty} f(n) \)
Simplification using highest degree terms

Theorems

Limits at infinity
Factorization for dominant terms

Suitable Grade Level

College level (Calculus I or II)