Math Problem Statement

Find the limit of the sequence defined as L = lim (n→∞) S_n = lim (n→∞) (2n / (n + 3)).

Solution

The given mathematical expression appears to define the limit of a sequence SnS_n as nn \to \infty. Specifically:

L=limnSn=limn2nn+3.L = \lim_{n \to \infty} S_n = \lim_{n \to \infty} \frac{2n}{n+3}.

Let’s solve this limit step-by-step:

Step 1: Analyze the fraction

The sequence Sn=2nn+3S_n = \frac{2n}{n+3} is a rational function where the degree of the numerator and denominator is the same (both have degree 1 in nn).

Step 2: Divide numerator and denominator by the highest degree term (nn):

2nn+3=2nn(1+3n)=21+3n.\frac{2n}{n+3} = \frac{2n}{n \cdot \left(1 + \frac{3}{n}\right)} = \frac{2}{1 + \frac{3}{n}}.

Step 3: Take the limit as nn \to \infty:

As nn \to \infty, the term 3n0\frac{3}{n} \to 0. Therefore, the fraction simplifies to: limn21+3n=21+0=2.\lim_{n \to \infty} \frac{2}{1 + \frac{3}{n}} = \frac{2}{1 + 0} = 2.

Final Answer:

L=2.L = 2.

The sequence SnS_n converges to L=2L = 2 as nn \to \infty.


Would you like a detailed explanation of any step? Here are some related questions:

  1. What happens to terms like 3n\frac{3}{n} as nn \to \infty?
  2. How do limits of rational functions behave when the degrees of numerator and denominator are equal?
  3. Could we use L’Hôpital’s Rule to confirm this limit?
  4. What would happen if the numerator had a higher degree than the denominator?
  5. How can this method apply to other similar sequences?

Tip: For rational functions, always simplify by dividing numerator and denominator by the highest degree term in nn to find the limit.

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Math Problem Analysis

Mathematical Concepts

Calculus
Sequences
Limits
Rational Functions

Formulas

lim (n→∞) (an / bn) = a / b if degrees of an and bn are equal

Theorems

Limit of a rational function
Properties of limits at infinity

Suitable Grade Level

Grades 11-12