Math Problem Statement

Use the properties of limits to evaluate the limit if it exists.

lim is over x→7 (square root of (x) - 7/x - 49)

Solution

To evaluate the limit:

limx7x7x49\lim_{{x \to 7}} \frac{\sqrt{x} - 7}{x - 49}

First, let's analyze the form of the limit. When substituting x=7x = 7 directly:

77749=77749=00\frac{\sqrt{7} - 7}{7 - 49} = \frac{7 - 7}{7 - 49} = \frac{0}{0}

We get the indeterminate form 00\frac{0}{0}. Since this is indeterminate, we need to simplify the expression.

Step 1: Use Algebraic Manipulation (Rationalizing)

We can rationalize the numerator by multiplying both the numerator and denominator by the conjugate of the numerator:

x7x49x+7x+7\frac{\sqrt{x} - 7}{x - 49} \cdot \frac{\sqrt{x} + 7}{\sqrt{x} + 7}

This gives:

(x7)(x+7)(x49)(x+7)=x49(x49)(x+7)\frac{(\sqrt{x} - 7)(\sqrt{x} + 7)}{(x - 49)(\sqrt{x} + 7)} = \frac{x - 49}{(x - 49)(\sqrt{x} + 7)}

Step 2: Simplify the Expression

The x49x - 49 terms in the numerator and denominator cancel out, leaving:

1x+7\frac{1}{\sqrt{x} + 7}

Step 3: Evaluate the Limit

Now, substitute x=7x = 7 into the simplified expression:

17+7=17+7=114\frac{1}{\sqrt{7} + 7} = \frac{1}{7 + 7} = \frac{1}{14}

Thus, the value of the limit is:

limx7x7x49=114\lim_{{x \to 7}} \frac{\sqrt{x} - 7}{x - 49} = \frac{1}{14}

Would you like further clarification on this process, or any additional details?

Here are 5 related questions for further exploration:

  1. How do you rationalize expressions with different forms of radicals?
  2. Can limits always be solved by rationalizing the numerator?
  3. What is the significance of the indeterminate form 00\frac{0}{0}?
  4. How does L'Hôpital's Rule apply to limits like this one?
  5. How would the limit change if we had limxc\lim_{{x \to c}} where c7c \neq 7?

Tip: Always check for an indeterminate form like 00\frac{0}{0} or \frac{\infty}{\infty} before proceeding with limit evaluation, as it indicates further algebraic manipulation is necessary.

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Math Problem Analysis

Mathematical Concepts

Limits
Algebraic Manipulation
Indeterminate Forms

Formulas

lim (x → c) (f(x)/g(x))
Rationalization of radicals

Theorems

Limit Laws
Indeterminate Form Resolution

Suitable Grade Level

Grades 11-12