Math Problem Statement

Evaluate the limit lim(x → 2) [(x^2 - 8x + 12) / (x^2 + 4x - 12)].

Solution

The problem asks to evaluate the following limit:

limx2x28x+12x2+4x12.\lim_{x \to 2} \frac{x^2 - 8x + 12}{x^2 + 4x - 12}.

Step-by-step Solution:

  1. Substitute x=2x = 2 directly:

    Substitute x=2x = 2 into the expression:

    (2)28(2)+12(2)2+4(2)12=416+124+812=00.\frac{(2)^2 - 8(2) + 12}{(2)^2 + 4(2) - 12} = \frac{4 - 16 + 12}{4 + 8 - 12} = \frac{0}{0}.

    The result is an indeterminate form (00\frac{0}{0}), so further simplification is needed.

  2. Factor the numerator and denominator:

    • Factor the numerator x28x+12x^2 - 8x + 12:

      x28x+12=(x2)(x6).x^2 - 8x + 12 = (x - 2)(x - 6).

    • Factor the denominator x2+4x12x^2 + 4x - 12:

      x2+4x12=(x2)(x+6).x^2 + 4x - 12 = (x - 2)(x + 6).

  3. Simplify the expression:

    After factoring, the limit becomes:

    (x2)(x6)(x2)(x+6).\frac{(x - 2)(x - 6)}{(x - 2)(x + 6)}.

    Cancel the common factor (x2)(x - 2):

    x6x+6.\frac{x - 6}{x + 6}.

  4. Substitute x=2x = 2 again:

    Substitute x=2x = 2 into the simplified expression:

    262+6=48=12.\frac{2 - 6}{2 + 6} = \frac{-4}{8} = -\frac{1}{2}.

Final Answer:

12\boxed{-\frac{1}{2}}

Would you like more details or have any questions?

Related Questions:

  1. How do you handle indeterminate forms in limits?
  2. What are some techniques for factoring quadratic expressions?
  3. How do you find limits involving rational functions?
  4. What are the common mistakes to avoid when simplifying limits?
  5. How do you use L'Hôpital's Rule to solve indeterminate limits?

Tip:

Always try to factor and simplify before substituting values in limits to avoid indeterminate forms!

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Math Problem Analysis

Mathematical Concepts

Limits
Factoring Quadratic Equations
Indeterminate Forms

Formulas

Factoring: ax^2 + bx + c = (x - p)(x - q)
Limit laws: lim(x → c) f(x) / g(x)

Theorems

Limit Laws
Factoring Quadratics

Suitable Grade Level

High School to Early College (Grades 11-12 or Calculus I)