Math Problem Statement

lim (x^2 - 9) / (x^2 - x - 12) as x approaches -3

Solution

The limit problem in the image is:

limx3x29x2x12\lim_{{x \to -3}} \frac{x^2 - 9}{x^2 - x - 12}

Let's solve it step by step.

Step 1: Factor both the numerator and the denominator

  • The numerator x29x^2 - 9 is a difference of squares: x29=(x3)(x+3)x^2 - 9 = (x - 3)(x + 3)

  • The denominator x2x12x^2 - x - 12 can be factored by finding two numbers that multiply to 12-12 and add to 1-1. These numbers are 4-4 and 33: x2x12=(x4)(x+3)x^2 - x - 12 = (x - 4)(x + 3)

Step 2: Simplify the expression

Now substitute the factored forms: (x3)(x+3)(x4)(x+3)\frac{(x - 3)(x + 3)}{(x - 4)(x + 3)}

Cancel out the common factor (x+3)(x + 3) from both the numerator and the denominator (as long as x3x \neq -3, which is true as we're taking a limit): x3x4\frac{x - 3}{x - 4}

Step 3: Evaluate the limit

Now, evaluate the limit as x3x \to -3: limx3x3x4=3334=67=67\lim_{{x \to -3}} \frac{x - 3}{x - 4} = \frac{-3 - 3}{-3 - 4} = \frac{-6}{-7} = \frac{6}{7}

Thus, the value of the limit is:

67\boxed{\frac{6}{7}}

Would you like any further details or have any questions about this solution?


Here are 5 related questions to expand on this topic:

  1. How do you handle limits when the expression includes a square root?
  2. What is the difference between solving limits algebraically and using L'Hopital's Rule?
  3. How would the solution change if the limit approached a different number?
  4. Can you explain how limits apply to continuity in calculus?
  5. What happens if direct substitution in the limit leads to a zero in the denominator?

Tip: When factoring quadratics, always check for common factoring techniques like difference of squares or simple factorization rules.

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Math Problem Analysis

Mathematical Concepts

Limits
Factoring
Simplification

Formulas

Difference of squares: a^2 - b^2 = (a - b)(a + b)
Factoring quadratics: ax^2 + bx + c = (x + p)(x + q)

Theorems

Limit Laws
Factoring Quadratics

Suitable Grade Level

Grades 10-12