Math Problem Statement

Determine whether the sequence a_n = ln(3n + 1) - ln(6n) converges or diverges. If it is convergent, find its limit.

Solution

To determine whether the sequence an=ln(3n+1)ln(6n)a_n = \ln(3n + 1) - \ln(6n) converges or diverges, we need to find the limit:

limnan=limn(ln(3n+1)ln(6n)).\lim_{n \to \infty} a_n = \lim_{n \to \infty} \left(\ln(3n + 1) - \ln(6n)\right).

Step 1: Simplify the expression

Using the properties of logarithms, we can combine the terms:

an=ln(3n+16n).a_n = \ln\left(\frac{3n + 1}{6n}\right).

Step 2: Simplify the fraction inside the logarithm

3n+16n=3n6n+16n=12+16n.\frac{3n + 1}{6n} = \frac{3n}{6n} + \frac{1}{6n} = \frac{1}{2} + \frac{1}{6n}.

As nn \to \infty, the term 16n0\frac{1}{6n} \to 0. Therefore:

limn3n+16n=12.\lim_{n \to \infty} \frac{3n + 1}{6n} = \frac{1}{2}.

Step 3: Take the limit

limnan=limnln(3n+16n)=ln(12)=ln(2).\lim_{n \to \infty} a_n = \lim_{n \to \infty} \ln\left(\frac{3n + 1}{6n}\right) = \ln\left(\frac{1}{2}\right) = -\ln(2).

Conclusion:

The limit exists and is equal to ln(2)-\ln(2). Therefore, the sequence converges to ln(2)-\ln(2).

Answer: limnan=ln(2),\lim_{n \to \infty} a_n = -\ln(2), and the sequence converges.

Would you like more details or have any questions?

Related Questions:

  1. What is the general approach to finding the limit of a sequence involving logarithms?
  2. How can you use L'Hopital's Rule to find the limit of a sequence if needed?
  3. What does it mean for a sequence to converge, and how is it different from diverging?
  4. Can you explain how properties of logarithms help simplify expressions?
  5. How do we handle sequences where the terms inside a logarithm approach zero?

Tip: When working with logarithmic sequences, always try to simplify expressions using logarithmic properties to make the limit evaluation easier.

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Math Problem Analysis

Mathematical Concepts

Limits
Logarithms
Sequences
Asymptotic Behavior

Formulas

ln(a) - ln(b) = ln(a/b)
Limit properties: lim n→∞ (3n + 1) / 6n = 1/2

Theorems

Properties of Logarithms
Limit Laws for Sequences

Suitable Grade Level

Grades 11-12