Math Problem Statement

solve it

lim (x→0) [sqrt(x+2) - sqrt(2)] / [x(1+x)]

Solution

We are tasked with solving the following limit:

limx0x+22x(1+x).\lim_{x \to 0} \frac{\sqrt{x+2} - \sqrt{2}}{x(1+x)}.


Step 1: Simplify the numerator

The numerator involves a difference of square roots:
x+22.\sqrt{x+2} - \sqrt{2}.
To simplify, multiply and divide by the conjugate:
x+22x+22x+2+2x+2+2=(x+2)2(2)2x+2+2.\frac{\sqrt{x+2} - \sqrt{2}}{\sqrt{x+2} - \sqrt{2}} \cdot \frac{\sqrt{x+2} + \sqrt{2}}{\sqrt{x+2} + \sqrt{2}} = \frac{(\sqrt{x+2})^2 - (\sqrt{2})^2}{\sqrt{x+2} + \sqrt{2}}.

This simplifies to:
(x+2)2x+2+2=xx+2+2.\frac{(x+2) - 2}{\sqrt{x+2} + \sqrt{2}} = \frac{x}{\sqrt{x+2} + \sqrt{2}}.

Thus, the numerator becomes:
x+22=xx+2+2.\sqrt{x+2} - \sqrt{2} = \frac{x}{\sqrt{x+2} + \sqrt{2}}.


Step 2: Rewrite the full expression

Substitute the simplified numerator into the original limit:
limx0x+22x(1+x)=limx0xx+2+2x(1+x).\lim_{x \to 0} \frac{\sqrt{x+2} - \sqrt{2}}{x(1+x)} = \lim_{x \to 0} \frac{\frac{x}{\sqrt{x+2} + \sqrt{2}}}{x(1+x)}.

Simplify the fraction by dividing xx out:
limx0xx+2+21x(1+x)=limx01(x+2+2)(1+x).\lim_{x \to 0} \frac{x}{\sqrt{x+2} + \sqrt{2}} \cdot \frac{1}{x(1+x)} = \lim_{x \to 0} \frac{1}{(\sqrt{x+2} + \sqrt{2})(1+x)}.


Step 3: Evaluate the limit as x0x \to 0

As x0x \to 0, the terms simplify as follows:

  • x+22\sqrt{x+2} \to \sqrt{2},
  • 1+x11 + x \to 1.

Thus, the denominator becomes:
(x+2+2)(1+x)(2+2)(1)=22.(\sqrt{x+2} + \sqrt{2})(1+x) \to (\sqrt{2} + \sqrt{2})(1) = 2\sqrt{2}.


Final Answer:

limx0x+22x(1+x)=122.\lim_{x \to 0} \frac{\sqrt{x+2} - \sqrt{2}}{x(1+x)} = \frac{1}{2\sqrt{2}}.


Do you want further clarifications or details on any step?

Here are 5 related questions to explore:

  1. How can we generalize limits involving square roots and conjugates?
  2. What happens if we encounter xax \to a instead of x0x \to 0?
  3. How does multiplying by conjugates simplify expressions?
  4. Can L'Hôpital's Rule also solve this limit?
  5. How do we handle more complex roots in limits?

Tip: When dealing with square roots in limits, multiplying by the conjugate is a key strategy to simplify the expression.

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Math Problem Analysis

Mathematical Concepts

Limits
Simplifying square root expressions
Conjugates in algebra

Formulas

Difference of squares: (a^2 - b^2) = (a - b)(a + b)
Conjugate multiplication for square roots

Theorems

Limit evaluation using conjugates

Suitable Grade Level

Undergraduate Calculus or Advanced High School