Math Problem Statement

Use the intuitive approach to explain why the limit \lim_{x\rarr2\text{ }} $$$$ \frac{x^2-4}{x-2}exists, and compute the limit.

Solution

Let's explore the limit using an intuitive approach.

We are asked to find the limit:

limx2x24x2\lim_{x \to 2} \frac{x^2 - 4}{x - 2}

Step 1: Substitute x=2x = 2

First, let's try plugging x=2x = 2 directly into the expression:

22422=440=00\frac{2^2 - 4}{2 - 2} = \frac{4 - 4}{0} = \frac{0}{0}

This results in the indeterminate form 00\frac{0}{0}. It means we cannot directly compute the limit by simple substitution, but it also suggests that we might be able to simplify the expression.

Step 2: Simplify the expression

The numerator, x24x^2 - 4, is a difference of squares. We can factor it as:

x24=(x2)(x+2)x^2 - 4 = (x - 2)(x + 2)

So, the original expression becomes:

x24x2=(x2)(x+2)x2\frac{x^2 - 4}{x - 2} = \frac{(x - 2)(x + 2)}{x - 2}

Now, for x2x \neq 2, we can cancel the common factor x2x - 2 from both the numerator and the denominator:

(x2)(x+2)x2=x+2forx2\frac{(x - 2)(x + 2)}{x - 2} = x + 2 \quad \text{for} \quad x \neq 2

Step 3: Evaluate the limit of the simplified expression

Now that we have simplified the expression to x+2x + 2, we can substitute x=2x = 2 without any issues:

limx2(x+2)=2+2=4\lim_{x \to 2} (x + 2) = 2 + 2 = 4

Conclusion:

Therefore, the limit exists and its value is:

limx2x24x2=4\lim_{x \to 2} \frac{x^2 - 4}{x - 2} = 4

Why does the limit exist?

The indeterminate form 00\frac{0}{0} indicates that the function has a removable discontinuity at x=2x = 2. After simplifying the expression, the discontinuity is "removed," and we are left with a continuous function x+2x + 2, which has no problems at x=2x = 2. This is why the limit exists and equals 4.


Would you like further details or have any questions?

Here are 5 related questions:

  1. How do we handle other indeterminate forms like 00\frac{0}{0}?
  2. What is the difference between a removable and non-removable discontinuity?
  3. How does factoring help in solving limits involving polynomials?
  4. Can limits be used to define continuity of a function?
  5. How does L'Hopital's rule apply to indeterminate forms like 00\frac{0}{0}?

Tip: When dealing with indeterminate forms, always look for algebraic simplifications such as factoring, rationalizing, or canceling common terms.

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Math Problem Analysis

Mathematical Concepts

Limits
Indeterminate Forms
Factoring
Difference of Squares

Formulas

Difference of squares: x^2 - a^2 = (x - a)(x + a)

Theorems

Limit laws
Removable discontinuity

Suitable Grade Level

Grades 11-12 or College Calculus