Math Problem Statement

lim_{x->2} \frac{x^3 - 8}{x^2 - 3x + 2}

Solution

This is a limit problem. You are asked to compute:

limx2x38x23x+2.\lim_{x \to 2} \frac{x^3 - 8}{x^2 - 3x + 2}.

Step 1: Check for indeterminate form

When x=2x = 2, substitute into both the numerator and denominator:

  • Numerator: x38=238=0x^3 - 8 = 2^3 - 8 = 0,
  • Denominator: x23x+2=223(2)+2=46+2=0x^2 - 3x + 2 = 2^2 - 3(2) + 2 = 4 - 6 + 2 = 0.

Since both the numerator and denominator are 0, this is an indeterminate form (0/00/0). We need to simplify the expression.


Step 2: Factorize the numerator and denominator

Numerator: x38x^3 - 8

This is a difference of cubes: x38=(x2)(x2+2x+4).x^3 - 8 = (x - 2)(x^2 + 2x + 4).

Denominator: x23x+2x^2 - 3x + 2

This is a quadratic trinomial that factors as: x23x+2=(x1)(x2).x^2 - 3x + 2 = (x - 1)(x - 2).


Step 3: Simplify the expression

The original limit becomes: x38x23x+2=(x2)(x2+2x+4)(x1)(x2).\frac{x^3 - 8}{x^2 - 3x + 2} = \frac{(x - 2)(x^2 + 2x + 4)}{(x - 1)(x - 2)}.

Cancel the common factor (x2)(x - 2) (valid as long as x2x \neq 2): x2+2x+4x1.\frac{x^2 + 2x + 4}{x - 1}.


Step 4: Evaluate the limit

Now, substitute x=2x = 2 into the simplified expression: x2+2x+4x1=22+2(2)+421=4+4+41=121=12.\frac{x^2 + 2x + 4}{x - 1} = \frac{2^2 + 2(2) + 4}{2 - 1} = \frac{4 + 4 + 4}{1} = \frac{12}{1} = 12.


Final Answer:

limx2x38x23x+2=12.\lim_{x \to 2} \frac{x^3 - 8}{x^2 - 3x + 2} = 12.

Would you like further clarifications or additional examples?


5 Related Questions:

  1. How do you handle limits with indeterminate forms like 00\frac{0}{0}?
  2. What are the steps to factor a difference of cubes like x3a3x^3 - a^3?
  3. How do you factor quadratic expressions like x23x+2x^2 - 3x + 2?
  4. What happens if there are higher-order indeterminate forms (e.g., \frac{\infty}{\infty})?
  5. How does the cancellation of terms affect the domain of the function?

Tip:

Always check for possible factorization in limit problems to resolve indeterminate forms.

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Math Problem Analysis

Mathematical Concepts

Limits
Algebraic Factorization
Indeterminate Forms

Formulas

Difference of Cubes: a^3 - b^3 = (a - b)(a^2 + ab + b^2)
Factoring Quadratic Equations: x^2 - 3x + 2 = (x - 1)(x - 2)

Theorems

Limit Simplification: Cancel terms after factoring to resolve indeterminate forms.

Suitable Grade Level

Grades 11-12