Math Problem Statement

lim x→2 x 3−8 3x2−6x

Solution

The given limit expression is:

limx2x383x26x\lim_{{x \to 2}} \frac{{x^3 - 8}}{{3x^2 - 6x}}

To solve this, we can follow these steps:

Step 1: Check for direct substitution

First, try substituting x=2x = 2 into the expression:

2383(22)6(2)=883(4)12=00\frac{{2^3 - 8}}{{3(2^2) - 6(2)}} = \frac{{8 - 8}}{{3(4) - 12}} = \frac{0}{0}

Since this results in an indeterminate form 00\frac{0}{0}, we need to simplify the expression further.

Step 2: Factor the numerator and denominator

  • The numerator x38x^3 - 8 is a difference of cubes. This can be factored as:

x38=(x2)(x2+2x+4)x^3 - 8 = (x - 2)(x^2 + 2x + 4)

  • The denominator 3x26x3x^2 - 6x can be factored as:

3x26x=3x(x2)3x^2 - 6x = 3x(x - 2)

Step 3: Simplify the expression

Now substitute the factored forms into the original limit:

limx2(x2)(x2+2x+4)3x(x2)\lim_{{x \to 2}} \frac{{(x - 2)(x^2 + 2x + 4)}}{{3x(x - 2)}}

We can cancel the (x2)(x - 2) terms from the numerator and denominator, assuming x2x \neq 2:

limx2x2+2x+43x\lim_{{x \to 2}} \frac{{x^2 + 2x + 4}}{{3x}}

Step 4: Apply direct substitution again

Now, substitute x=2x = 2 into the simplified expression:

22+2(2)+43(2)=4+4+46=126=2\frac{{2^2 + 2(2) + 4}}{{3(2)}} = \frac{{4 + 4 + 4}}{{6}} = \frac{{12}}{{6}} = 2

Final Answer:

limx2x383x26x=2\lim_{{x \to 2}} \frac{{x^3 - 8}}{{3x^2 - 6x}} = 2

Would you like more details or further clarification?

Here are some additional questions related to this concept:

  1. How do you solve limits involving indeterminate forms other than 00\frac{0}{0}?
  2. What is the factorization process for cubes and squares in polynomials?
  3. Can you explain why cancelling terms like (x2)(x - 2) is valid?
  4. How do you apply L'Hopital's Rule to solve limits?
  5. What are common indeterminate forms in limits, and how can we simplify them?

Tip: Always check for factorization possibilities when you encounter indeterminate forms like 00\frac{0}{0}.

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Math Problem Analysis

Mathematical Concepts

Calculus
Limits
Factorization
Indeterminate Forms

Formulas

Factorization of a difference of cubes: a^3 - b^3 = (a - b)(a^2 + ab + b^2)
Factoring out common terms in polynomials

Theorems

Limit Laws
Difference of Cubes Theorem

Suitable Grade Level

Grades 11-12