Math Problem Statement

Use the intuitive approach to explain why the limit lim_{x -> 2} (x^3 - 8) / (x^2 - 4) exists, and compute the limit.

Solution

The problem asks to explain why the limit limx2x38x24\lim_{x \to 2} \frac{x^3 - 8}{x^2 - 4} exists and compute the limit using an intuitive approach.

Step-by-Step Solution:

1. Simplifying the expression:

The given expression is x38x24\frac{x^3 - 8}{x^2 - 4}.

We can factor both the numerator and the denominator:

  • The numerator x38x^3 - 8 is a difference of cubes: x38=(x2)(x2+2x+4)x^3 - 8 = (x - 2)(x^2 + 2x + 4)
  • The denominator x24x^2 - 4 is a difference of squares: x24=(x2)(x+2)x^2 - 4 = (x - 2)(x + 2)

Now, rewrite the expression: (x2)(x2+2x+4)(x2)(x+2)\frac{(x - 2)(x^2 + 2x + 4)}{(x - 2)(x + 2)}

2. Cancelling the common factor:

For x2x \neq 2, we can cancel the (x2)(x - 2) term from both the numerator and the denominator: x2+2x+4x+2\frac{x^2 + 2x + 4}{x + 2}

3. Substituting x=2x = 2:

Now, substitute x=2x = 2 into the simplified expression: 22+2(2)+42+2=4+4+44=124=3\frac{2^2 + 2(2) + 4}{2 + 2} = \frac{4 + 4 + 4}{4} = \frac{12}{4} = 3

Thus, the limit is 3\boxed{3}.

Why does the limit exist?

The limit exists because, after simplifying the expression by cancelling the removable discontinuity at x=2x = 2, the resulting function x2+2x+4x+2\frac{x^2 + 2x + 4}{x + 2} is continuous at x=2x = 2. Therefore, we can evaluate the limit by direct substitution.

Would you like more details or explanations?

Here are 5 related questions for further practice:

  1. How would the solution change if the denominator were x2+4x^2 + 4 instead of x24x^2 - 4?
  2. How can you apply L'Hôpital's Rule to solve this limit?
  3. What is the geometrical interpretation of cancelling common factors in limits?
  4. Can you find the limit if the expression were limx2x38x24\lim_{x \to -2} \frac{x^3 - 8}{x^2 - 4}?
  5. How would the factorization change if the numerator were x3+8x^3 + 8 instead of x38x^3 - 8?

Tip: Always check for common factors to simplify limits with indeterminate forms, like 00\frac{0}{0}.

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Limits
Factoring Polynomials
Rational Functions

Formulas

x^3 - a^3 = (x - a)(x^2 + ax + a^2)
x^2 - a^2 = (x - a)(x + a)

Theorems

Limit Existence via Simplification
Removable Discontinuity

Suitable Grade Level

Grades 10-12