Finding the Values that Make the Denominator Equal to Zero

Oct 13, 2025 by wbrum.org 136 views

Introduction

Rational functions are a fundamental concept in algebra and mathematics, representing the ratio of two polynomials. In this article, we will delve into the analysis of a given rational function, performing tasks such as finding intercepts, determining the domain, identifying vertical or horizontal asymptotes, and graphing the function using a graphing calculator.

Task (A): Finding the Intercepts for the Graph

To find the intercepts of the graph, we need to determine the points where the function intersects the x-axis (x-intercepts) and the y-axis (y-intercept).

Finding the X-Intercepts

The x-intercepts occur when the function is equal to zero. To find the x-intercepts, we set the numerator of the rational function equal to zero and solve for x.

f(x) = \frac{x^2 - 4}{x^2 - 9}

Setting the numerator equal to zero:

x^2 - 4 = 0

Solving for x:

x^2 = 4
x = \pm 2

Therefore, the x-intercepts are (2, 0) and (-2, 0).

Finding the Y-Intercept

The y-intercept occurs when x is equal to zero. To find the y-intercept, we substitute x = 0 into the function.

f(0) = \frac{0^2 - 4}{0^2 - 9}
f(0) = \frac{-4}{-9}
f(0) = \frac{4}{9}

Therefore, the y-intercept is (0, 4/9).

Task (B): Determining the Domain

The domain of a rational function is the set of all possible input values (x) for which the function is defined. In the case of a rational function, the domain is all real numbers except for the values that make the denominator equal to zero.

Finding the Values that Make the Denominator Equal to Zero

To find the values that make the denominator equal to zero, we set the denominator equal to zero and solve for x.

x^2 - 9 = 0

Solving for x:

x^2 = 9
x = \pm 3

Therefore, the values that make the denominator equal to zero are x = 3 and x = -3.

Determining the Domain

Since the denominator cannot be equal to zero, we must exclude x = 3 and x = -3 from the domain. Therefore, the domain of the function is all real numbers except for x = 3 and x = -3.

Task (C): Finding Any Vertical or Horizontal Asymptotes

Vertical asymptotes occur when the denominator of the rational function is equal to zero, and the numerator is not equal to zero. Horizontal asymptotes occur when the degree of the numerator is equal to the degree of the denominator.

Finding the Vertical Asymptotes

We have already found the values that make the denominator equal to zero, which are x = 3 and x = -3. Therefore, the vertical asymptotes are x = 3 and x = -3.

Finding the Horizontal Asymptotes

To find the horizontal asymptotes, we compare the degree of the numerator and the degree of the denominator.

f(x) = \frac{x^2 - 4}{x^2 - 9}

The degree of the numerator is 2, and the degree of the denominator is also 2. Since the degree of the numerator is equal to the degree of the denominator, we can conclude that there is a horizontal asymptote at y = 1.

Task (D): Graphing the Function Using a Graphing Calculator

To graph the function using a graphing calculator, we need to enter the function into the calculator and adjust the window settings to display the graph.

f(x) = \frac{x^2 - 4}{x^2 - 9}

Using a graphing calculator, we can graph the function and observe the intercepts, domain, vertical and horizontal asymptotes, and other features of the graph.

Conclusion

In this article, we performed tasks such as finding intercepts, determining the domain, identifying vertical or horizontal asymptotes, and graphing the function using a graphing calculator for a given rational function. We found the x-intercepts, y-intercept, domain, vertical asymptotes, and horizontal asymptotes, and graphed the function using a graphing calculator. This analysis provides a comprehensive understanding of the rational function and its graph.

References

[1] "Rational Functions" by Math Open Reference. Retrieved from https://www.mathopenref.com/rationalfunctions.html
[2] "Graphing Rational Functions" by Khan Academy. Retrieved from https://www.khanacademy.org/math/algebra2/x2f2f7c7/x2f2f7c7-graphing-rational-functions/v/graphing-rational-functions
[3] "Rational Functions" by Wolfram MathWorld. Retrieved from https://mathworld.wolfram.com/RationalFunction.html

Introduction

In the previous article, we performed tasks such as finding intercepts, determining the domain, identifying vertical or horizontal asymptotes, and graphing the function using a graphing calculator for a given rational function. In this article, we will address some common questions and concerns related to rational function analysis.

Q&A

Q: What is the difference between a rational function and a polynomial function?

A: A rational function is a function that can be expressed as the ratio of two polynomials, while a polynomial function is a function that can be expressed as a sum of terms, each of which is a constant or a product of a constant and a variable raised to a non-negative integer power.

Q: How do I determine the domain of a rational function?

A: To determine the domain of a rational function, you need to find the values of x that make the denominator equal to zero and exclude those values from the domain.

Q: What is the difference between a vertical asymptote and a horizontal asymptote?

A: A vertical asymptote is a line that the graph of a function approaches as the input values get arbitrarily close to a certain value, while a horizontal asymptote is a horizontal line that the graph of a function approaches as the input values get arbitrarily large.

Q: How do I find the x-intercepts of a rational function?

A: To find the x-intercepts of a rational function, you need to set the numerator equal to zero and solve for x.

Q: What is the significance of the degree of the numerator and the degree of the denominator in a rational function?

A: The degree of the numerator and the degree of the denominator in a rational function determine the horizontal asymptote of the function. If the degree of the numerator is equal to the degree of the denominator, then the horizontal asymptote is the ratio of the leading coefficients of the numerator and the denominator.

Q: How do I graph a rational function using a graphing calculator?

A: To graph a rational function using a graphing calculator, you need to enter the function into the calculator and adjust the window settings to display the graph.

Q: What are some common mistakes to avoid when analyzing rational functions?

A: Some common mistakes to avoid when analyzing rational functions include:

Not checking for vertical asymptotes
Not checking for horizontal asymptotes
Not checking for x-intercepts
Not checking for domain restrictions
Not using a graphing calculator to visualize the graph

Q: How do I determine the behavior of a rational function as x approaches positive or negative infinity?

A: To determine the behavior of a rational function as x approaches positive or negative infinity, you need to compare the degree of the numerator and the degree of the denominator. If the degree of the numerator is equal to the degree of the denominator, then the function approaches the ratio of the leading coefficients of the numerator and the denominator as x approaches positive or negative infinity.

Conclusion

In this article, we addressed some common questions and concerns related to rational function analysis. We discussed the difference between a rational function and a polynomial function, how to determine the domain of a rational function, the difference between a vertical asymptote and a horizontal asymptote, and how to graph a rational function using a graphing calculator. We also discussed some common mistakes to avoid when analyzing rational functions and how to determine the behavior of a rational function as x approaches positive or negative infinity.

References

[1] "Rational Functions" by Math Open Reference. Retrieved from https://www.mathopenref.com/rationalfunctions.html
[2] "Graphing Rational Functions" by Khan Academy. Retrieved from https://www.khanacademy.org/math/algebra2/x2f2f7c7/x2f2f7c7-graphing-rational-functions/v/graphing-rational-functions
[3] "Rational Functions" by Wolfram MathWorld. Retrieved from https://mathworld.wolfram.com/RationalFunction.html