Math Problem Statement

If f(x) = ln(x), then lim x→3 (f(x) - f(3)) / (x - 3)

Solution

The problem involves finding the limit:

limx3f(x)f(3)x3\lim_{x \to 3} \frac{f(x) - f(3)}{x - 3}

Given that f(x)=ln(x)f(x) = \ln(x), this expression can be identified as the definition of the derivative of f(x)f(x) at x=3x = 3.

Steps:

  1. Definition of derivative:

    The derivative of a function f(x)f(x) at a point aa is given by:

    f(a)=limxaf(x)f(a)xaf'(a) = \lim_{x \to a} \frac{f(x) - f(a)}{x - a}

    Here, f(x)=ln(x)f(x) = \ln(x) and a=3a = 3. So the given limit represents f(3)f'(3).

  2. Derivative of f(x)=ln(x)f(x) = \ln(x):

    We know that the derivative of ln(x)\ln(x) is:

    f(x)=1xf'(x) = \frac{1}{x}

  3. Evaluating at x=3x = 3:

    f(3)=13f'(3) = \frac{1}{3}

Thus, the limit is:

limx3ln(x)ln(3)x3=13\lim_{x \to 3} \frac{\ln(x) - \ln(3)}{x - 3} = \frac{1}{3}

Final answer:

13\boxed{\frac{1}{3}}

Would you like further details or have any questions about this problem?

Here are 5 related questions for further exploration:

  1. How would you compute the derivative of ln(x)\ln(x) using first principles?
  2. What is the geometric interpretation of this limit?
  3. How does this problem change if f(x)f(x) were a different logarithmic function?
  4. Can you apply L'Hôpital's Rule to solve this limit?
  5. How would you calculate the derivative of ln(x)\ln(x) at any arbitrary point aa?

Tip: When faced with a limit resembling the difference quotient, always check if it represents the derivative of a function at a specific point.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Limits
Derivatives
Logarithmic Functions

Formulas

f'(a) = lim x→a (f(x) - f(a)) / (x - a)
Derivative of ln(x): f'(x) = 1/x

Theorems

Definition of Derivative
Logarithmic Differentiation

Suitable Grade Level

Grades 10-12 or early college