Math Problem Statement

Which of the following describes the behavior of the function r(x) = 5x / (x - 8) near its asymptote?

Solution

We are given the function r(x)=5xx8r(x) = \frac{5x}{x - 8} and are asked to determine its behavior near the vertical asymptote x=8x = 8. Specifically, we are looking for the one-sided limits as xx approaches 8 from the left (x8x \to 8^-) and from the right (x8+x \to 8^+).

Step-by-step analysis:

  1. For x8x \to 8^- (approaching 8 from the left):

    • As xx approaches 8 from the left, x8x - 8 becomes a small negative number (since values of xx are slightly less than 8).
    • Therefore, the denominator x8x - 8 will approach 00^- (a small negative number).
    • The numerator 5x5x will approach 5(8)=405(8) = 40, which is positive.
    • So, the whole fraction approaches 400\frac{40}{0^-}, which tends to -\infty.

    Thus, limx8r(x)=\lim_{x \to 8^-} r(x) = -\infty.

  2. For x8+x \to 8^+ (approaching 8 from the right):

    • As xx approaches 8 from the right, x8x - 8 becomes a small positive number (since values of xx are slightly more than 8).
    • Therefore, the denominator x8x - 8 will approach 0+0^+ (a small positive number).
    • The numerator 5x5x will approach 4040, which is positive.
    • So, the whole fraction approaches 400+\frac{40}{0^+}, which tends to ++\infty.

    Thus, limx8+r(x)=+\lim_{x \to 8^+} r(x) = +\infty.

Conclusion:

The correct option describes the behavior as: limx8r(x)=andlimx8+r(x)=+.\lim_{x \to 8^-} r(x) = -\infty \quad \text{and} \quad \lim_{x \to 8^+} r(x) = +\infty. This corresponds to the last option in the image.

Would you like a detailed explanation of why vertical asymptotes behave this way? Here are five related questions to explore this topic further:

  1. How do you identify the location of vertical asymptotes in a rational function?
  2. What happens to the graph of a function near its vertical asymptote?
  3. Can a function have more than one vertical asymptote?
  4. What is the difference between vertical and horizontal asymptotes?
  5. How do you calculate limits involving infinity for more complex rational functions?

Tip: Always remember that vertical asymptotes occur where the denominator approaches zero but the numerator does not.

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Math Problem Analysis

Mathematical Concepts

Limits
Rational Functions
Asymptotes

Formulas

Limit formula for rational functions approaching a vertical asymptote

Theorems

Limit Theorem for Rational Functions
Vertical Asymptote Behavior

Suitable Grade Level

Grades 11-12