Math Problem Statement

Find the limit of \( \lim_{x \to \infty} \frac{-7x}{\sqrt{4x^2 - 3}} \).

Solution

This is a mathematical limit problem. The goal is to find:

limx7x4x23\lim_{x \to \infty} \frac{-7x}{\sqrt{4x^2 - 3}}

Step-by-step Solution:

  1. Factor out x2x^2 from the denominator: In the square root, factor x2x^2 from the terms inside: 4x23=x2(43x2)=x43x2\sqrt{4x^2 - 3} = \sqrt{x^2 (4 - \frac{3}{x^2})} = |x| \sqrt{4 - \frac{3}{x^2}} For xx \to \infty, x=x|x| = x (since x>0x > 0).

    So: 4x23=x43x2\sqrt{4x^2 - 3} = x \sqrt{4 - \frac{3}{x^2}}

  2. Rewrite the limit: Substitute the simplified denominator back into the fraction: 7x4x23=7xx43x2=743x2\frac{-7x}{\sqrt{4x^2 - 3}} = \frac{-7x}{x \sqrt{4 - \frac{3}{x^2}}} = \frac{-7}{\sqrt{4 - \frac{3}{x^2}}}

  3. Simplify as xx \to \infty: As xx \to \infty, the term 3x20\frac{3}{x^2} \to 0. Therefore: 43x24=2\sqrt{4 - \frac{3}{x^2}} \to \sqrt{4} = 2

    So, the fraction becomes: 743x272\frac{-7}{\sqrt{4 - \frac{3}{x^2}}} \to \frac{-7}{2}

Final Answer:

limx7x4x23=72\lim_{x \to \infty} \frac{-7x}{\sqrt{4x^2 - 3}} = -\frac{7}{2}


Would you like more details or have any questions?


Related Questions:

  1. What happens to the limit if the numerator is 7x7x instead of 7x-7x?
  2. How does factoring help simplify expressions involving square roots?
  3. Why does x=x|x| = x for x>0x > 0?
  4. How can we handle limits involving x2+a\sqrt{x^2 + a} as xx \to \infty?
  5. Can L'Hôpital's Rule be applied to this problem? Why or why not?

Tip:

Always check if terms like x2a\sqrt{x^2 - a} can be simplified by factoring out x2x^2, as it often simplifies limits involving infinity.

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Math Problem Analysis

Mathematical Concepts

Limits
Simplification of Radical Expressions
Infinity Behavior in Functions

Formulas

Simplification: \( \sqrt{ax^2 - b} = x \sqrt{a - \frac{b}{x^2}} \) as \( x \to \infty \)
Limit Evaluation: \( \lim_{x \to \infty} \frac{f(x)}{g(x)} \) using dominant terms

Theorems

Limits and Infinity
Properties of Square Roots

Suitable Grade Level

Grades 11-12