Math Problem Statement

Apply L'Hôpital's Rule to evaluate the following limit: \( \lim_{x \to e} \frac{1 - \frac{x}{e}}{\frac{x}{e} - 1} \).

Solution

To solve this limit using L'Hôpital's Rule, we need to verify that the expression forms an indeterminate type like 00\frac{0}{0} or \frac{\infty}{\infty}. Let's proceed step-by-step:

Step 1: Analyze the Indeterminate Form

The expression is: limxe1xexe1\lim_{x \to e} \frac{1 - \frac{x}{e}}{\frac{x}{e} - 1}

As xex \to e:

  • The numerator approaches 1ee=11=01 - \frac{e}{e} = 1 - 1 = 0.
  • The denominator approaches ee1=11=0\frac{e}{e} - 1 = 1 - 1 = 0.

This forms a 00\frac{0}{0} indeterminate form, so L'Hôpital's Rule applies.

Step 2: Apply L'Hôpital's Rule (First Application)

Using L'Hôpital's Rule, we take the derivatives of the numerator and the denominator with respect to xx:

  • The derivative of the numerator 1xe1 - \frac{x}{e} is 1e-\frac{1}{e}.
  • The derivative of the denominator xe1\frac{x}{e} - 1 is 1e\frac{1}{e}.

So, we get: limxe1e1e\lim_{x \to e} \frac{-\frac{1}{e}}{\frac{1}{e}}

Step 3: Simplify the Result

Simplifying this expression gives: 1e1e=1\frac{-\frac{1}{e}}{\frac{1}{e}} = -1

Final Answer

limxe1xexe1=1\lim_{x \to e} \frac{1 - \frac{x}{e}}{\frac{x}{e} - 1} = -1

Let me know if you would like further details on each step or have additional questions.

Here are five related questions for further practice:

  1. How is L'Hôpital's Rule derived, and why does it work for indeterminate forms?
  2. Can you apply L'Hôpital's Rule to limx0sinxx\lim_{x \to 0} \frac{\sin x}{x}?
  3. What are the limitations of using L'Hôpital's Rule?
  4. How would the process change if the expression was not in a 00\frac{0}{0} indeterminate form?
  5. How do you determine when to stop applying L'Hôpital's Rule in a problem?

Tip: When applying L'Hôpital's Rule, always double-check that the new form after differentiation still has an indeterminate form if you need to apply it multiple times.

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Math Problem Analysis

Mathematical Concepts

Calculus
Limits
Indeterminate Forms

Formulas

L'Hôpital's Rule: \( \lim_{x \to a} \frac{f(x)}{g(x)} = \lim_{x \to a} \frac{f'(x)}{g'(x)} \) if \( \frac{0}{0} \) or \( \frac{\infty}{\infty} \)

Theorems

L'Hôpital's Rule

Suitable Grade Level

Grades 11-12