Math Problem Statement

Solve

Evaluate the limits of the following expressions involving square roots and rational functions, and find the corresponding horizontal asymptotes.

Solution

Let's go through both limits from the image:

Problem (a):

You are asked to evaluate the limit: limx11+9x25+10x\lim_{x \to \infty} \frac{\sqrt{11 + 9x^2}}{5 + 10x}

Step 1: Simplify the expression for large xx

For large xx, the term 9x29x^2 dominates inside the square root. So, we approximate: 11+9x29x2=3xasx\sqrt{11 + 9x^2} \approx \sqrt{9x^2} = 3x \quad \text{as} \quad x \to \infty Thus, the expression simplifies to: 3x5+10x\frac{3x}{5 + 10x}

Step 2: Factor out xx from both the numerator and denominator

3x5+10x=3xx(10+5x)=310+5x\frac{3x}{5 + 10x} = \frac{3x}{x(10 + \frac{5}{x})} = \frac{3}{10 + \frac{5}{x}}

As xx \to \infty, 5x0\frac{5}{x} \to 0. So the limit becomes: limx310=310\lim_{x \to \infty} \frac{3}{10} = \frac{3}{10}

Thus, the limit for part (a) is 310\frac{3}{10}, and the corresponding horizontal asymptote is y=310y = \frac{3}{10}.


Problem (b):

You are asked to evaluate the limit: limx11+9x25+10x\lim_{x \to -\infty} \frac{\sqrt{11 + 9x^2}}{5 + 10x}

Step 1: Simplify the expression for large negative xx

Again, for large negative xx, the term 9x29x^2 dominates inside the square root. So, approximate: 11+9x23x=3(x)sincex\sqrt{11 + 9x^2} \approx 3|x| = 3(-x) \quad \text{since} \quad x \to -\infty Thus, the expression simplifies to: 3(x)5+10x\frac{3(-x)}{5 + 10x}

Step 2: Factor out xx

3(x)5+10x=3xx(10+5x)=310+5x\frac{3(-x)}{5 + 10x} = \frac{-3x}{x(10 + \frac{5}{x})} = \frac{-3}{10 + \frac{5}{x}}

As xx \to -\infty, 5x0\frac{5}{x} \to 0. So the limit becomes: limx310=310\lim_{x \to -\infty} \frac{-3}{10} = \frac{-3}{10}

Thus, the limit for part (b) is 310\frac{-3}{10}, and the corresponding horizontal asymptote is y=310y = \frac{-3}{10}.


Would you like more details on any of these steps? Here are five related questions you could explore:

  1. How do you find vertical asymptotes in rational functions?
  2. Why does 11+9x23x\sqrt{11 + 9x^2} \approx 3|x| for large xx?
  3. What is the significance of horizontal asymptotes in real-world applications?
  4. How does factoring out the dominant term help when calculating limits?
  5. How would these limits change if the expression had a different degree in the numerator or denominator?

Tip: When finding limits as xx approaches infinity, always check for dominant terms that grow the fastest in both the numerator and denominator.

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Math Problem Analysis

Mathematical Concepts

Limits
Asymptotes
Rational Functions
Square Roots
Infinity

Formulas

lim_{x → ∞} f(x)
Horizontal Asymptote: lim_{x → ∞} f(x) = L implies y = L
For large x, sqrt(a + bx^2) ≈ sqrt(b) * |x|

Theorems

Dominant Term Approximation for Limits at Infinity

Suitable Grade Level

Undergraduate Calculus or Advanced High School Calculus