Math Problem Statement

lim (x → 0) (sqrt(49 - x) - 7) / x

Solution

The given expression is:

limx049x7x\lim_{{x \to 0}} \frac{{\sqrt{49 - x} - 7}}{x}

Step-by-step solution:

This is an indeterminate form of 00\frac{0}{0} when directly substituting x=0x = 0. So, we need to manipulate the expression to resolve this.

1. Multiply by the conjugate:

We can multiply the numerator and denominator by the conjugate of the numerator to simplify the square root term. The conjugate of 49x7\sqrt{49 - x} - 7 is 49x+7\sqrt{49 - x} + 7.

limx049x7x×49x+749x+7=limx0(49x7)(49x+7)x(49x+7)\lim_{{x \to 0}} \frac{{\sqrt{49 - x} - 7}}{x} \times \frac{{\sqrt{49 - x} + 7}}{{\sqrt{49 - x} + 7}} = \lim_{{x \to 0}} \frac{{(\sqrt{49 - x} - 7)(\sqrt{49 - x} + 7)}}{{x(\sqrt{49 - x} + 7)}}

2. Simplify the numerator:

By applying the difference of squares formula (ab)(a+b)=a2b2(a - b)(a + b) = a^2 - b^2, we simplify the numerator:

(49x)272=(49x)49=x(\sqrt{49 - x})^2 - 7^2 = (49 - x) - 49 = -x

Thus, the expression becomes:

limx0xx(49x+7)=limx0149x+7\lim_{{x \to 0}} \frac{{-x}}{{x(\sqrt{49 - x} + 7)}} = \lim_{{x \to 0}} \frac{{-1}}{{\sqrt{49 - x} + 7}}

3. Evaluate the limit:

Now, substitute x=0x = 0 into the expression:

1490+7=17+7=114\frac{{-1}}{{\sqrt{49 - 0} + 7}} = \frac{{-1}}{{7 + 7}} = \frac{{-1}}{{14}}

Final Answer:

limx049x7x=114\lim_{{x \to 0}} \frac{{\sqrt{49 - x} - 7}}{x} = \frac{{-1}}{{14}}

Would you like further explanation on any step or more examples of limits?

Here are 5 related questions for further practice:

  1. How would you approach solving limx0x+11x\lim_{{x \to 0}} \frac{{\sqrt{x+1} - 1}}{x}?
  2. What is the limit of limx01cos(x)x2\lim_{{x \to 0}} \frac{{1 - \cos(x)}}{x^2}?
  3. Can you compute limx0sin(3x)x\lim_{{x \to 0}} \frac{{\sin(3x)}}{x}?
  4. How do we apply L'Hopital's Rule to solve limits of indeterminate forms?
  5. What are the different techniques for evaluating limits involving radicals?

Tip: Always check if a limit expression is in an indeterminate form before applying algebraic manipulations or L'Hopital's Rule!

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Math Problem Analysis

Mathematical Concepts

Limits
Radicals
Indeterminate Forms

Formulas

Difference of Squares: (a^2 - b^2) = (a - b)(a + b)
Limit Evaluation Techniques
Conjugate Multiplication

Theorems

Indeterminate Forms
Limit Laws

Suitable Grade Level

Grades 11-12