Math Problem Statement

Determine the domain and asymptotes of each rational function.

Solution

To analyze the given rational function y=4x2162x+9y = \frac{4x^2 - 16}{2x + 9}, we need to determine its domain and asymptotes.

1. Domain:

The domain of a rational function is all real numbers except where the denominator equals zero because division by zero is undefined.

The denominator of the function is 2x+92x + 9.

Set the denominator equal to zero and solve for xx:

2x+9=02x + 9 = 0

2x=92x = -9

x=92x = -\frac{9}{2}

So, the domain is all real numbers except x=92x = -\frac{9}{2}.

Domain: xR,x92x \in \mathbb{R}, x \neq -\frac{9}{2}

2. Vertical Asymptote:

Vertical asymptotes occur where the denominator equals zero and the numerator does not simultaneously equal zero.

From the domain calculation, the vertical asymptote is at x=92x = -\frac{9}{2}.

Vertical Asymptote: x=92x = -\frac{9}{2}

3. Horizontal Asymptote:

To find the horizontal asymptote, we compare the degrees of the numerator and the denominator:

  • The degree of the numerator 4x2164x^2 - 16 is 2.
  • The degree of the denominator 2x+92x + 9 is 1.

Since the degree of the numerator is greater than the degree of the denominator (2 > 1), there is no horizontal asymptote.

Horizontal Asymptote: None

4. Oblique Asymptote:

When the degree of the numerator is one more than the degree of the denominator, there is an oblique (or slant) asymptote. Here, the numerator's degree is 2 and the denominator's degree is 1, so an oblique asymptote exists.

To find the oblique asymptote, perform polynomial long division of the numerator by the denominator:

4x2162x+9\frac{4x^2 - 16}{2x + 9}

Performing the division:

  • Divide 4x24x^2 by 2x2x to get 2x2x.
  • Multiply 2x2x by 2x+92x + 9, resulting in 4x2+18x4x^2 + 18x.
  • Subtract 4x2+18x4x^2 + 18x from 4x2164x^2 - 16, yielding 18x16-18x - 16.
  • Divide 18x-18x by 2x2x to get 9-9.
  • Multiply 9-9 by 2x+92x + 9, resulting in 18x81-18x - 81.
  • Subtract 18x81-18x - 81 from 18x16-18x - 16, giving a remainder of 6565.

So, the oblique asymptote is:

y=2x9y = 2x - 9

Oblique Asymptote: y=2x9y = 2x - 9

Summary:

  • Domain: xR,x92x \in \mathbb{R}, x \neq -\frac{9}{2}
  • Vertical Asymptote: x=92x = -\frac{9}{2}
  • Horizontal Asymptote: None
  • Oblique Asymptote: y=2x9y = 2x - 9

Would you like a detailed explanation of any part of the solution? Here are some related questions you might consider:

  1. What is the significance of the vertical asymptote in graphing the function?
  2. How does the oblique asymptote affect the shape of the graph as xx approaches infinity?
  3. Can a function have both a horizontal and an oblique asymptote?
  4. How would you graph this function, given the asymptotes and the domain?
  5. What happens to the function as xx approaches the vertical asymptote?

Tip: When dealing with rational functions, always check for common factors between the numerator and denominator to simplify the function if possible, which can reveal removable discontinuities.

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Math Problem Analysis

Mathematical Concepts

Rational Functions
Domain
Asymptotes

Formulas

Division by zero conditions
Degree comparison for asymptotes

Theorems

Existence of vertical asymptotes
Conditions for horizontal and oblique asymptotes

Suitable Grade Level

High School