Math Problem Statement

Use L'Hôpital's Rule to evaluate the limit lim_{x -> -2} (x + 2) / (x^2 - 4).

Solution

To evaluate the limit

limx2x+2x24\lim_{x \to -2} \frac{x + 2}{x^2 - 4}

using L'Hôpital's Rule, we first check if the limit has an indeterminate form.

Step 1: Check for Indeterminate Form

Substituting x=2x = -2 in the expression:

2+2(2)24=044=00\frac{-2 + 2}{(-2)^2 - 4} = \frac{0}{4 - 4} = \frac{0}{0}

This is an indeterminate form, so we can apply L'Hôpital's Rule.

Step 2: Apply L'Hôpital's Rule

According to L'Hôpital's Rule, we take the derivative of the numerator and the denominator separately.

  1. Numerator: The derivative of x+2x + 2 is 11.
  2. Denominator: The derivative of x24x^2 - 4 is 2x2x.

So, we can rewrite the limit as:

limx212x\lim_{x \to -2} \frac{1}{2x}

Step 3: Substitute x=2x = -2 Again

Now we substitute x=2x = -2 into the simplified expression:

12(2)=14=14\frac{1}{2(-2)} = \frac{1}{-4} = -\frac{1}{4}

Final Answer

limx2x+2x24=14\lim_{x \to -2} \frac{x + 2}{x^2 - 4} = -\frac{1}{4}

Would you like further details on any part of this solution?


Here are some related questions for further exploration:

  1. How is L'Hôpital's Rule derived?
  2. What are other examples where L'Hôpital's Rule is used for limits?
  3. How can you determine when not to use L'Hôpital's Rule?
  4. How do you handle higher-order derivatives if the 0/00/0 form persists?
  5. Can L'Hôpital's Rule be applied to infinite limits?

Tip: Always confirm that a limit is in an indeterminate form (like 0/00/0 or /\infty/\infty) before applying L'Hôpital's Rule.

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Math Problem Analysis

Mathematical Concepts

Calculus
Limits
L'Hôpital's Rule

Formulas

L'Hôpital's Rule: lim_{x -> c} f(x) / g(x) = lim_{x -> c} f'(x) / g'(x) if indeterminate
Derivative of a polynomial

Theorems

L'Hôpital's Rule

Suitable Grade Level

College Level Calculus