Finding the Roots of the Denominator

Oct 13, 2025 by wbrum.org 35 views

Introduction

Rational functions are a fundamental concept in mathematics, and understanding their discontinuities is crucial for solving various mathematical problems. In this article, we will delve into the world of rational functions and explore the concept of discontinuities, specifically focusing on the function $f(x)=\frac{x+1}{6x^2-7x-3}$ . We will examine the statements provided and determine which one is true about the discontinuities of the function.

What are Discontinuities?

A discontinuity in a function occurs when the function is not defined at a particular point or when the function's graph has a gap or a break at that point. Discontinuities can be classified into three types: removable discontinuities, jump discontinuities, and infinite discontinuities.

Removable Discontinuities: These occur when the function is not defined at a point, but the limit of the function as x approaches that point exists. In other words, the function has a hole at that point.
Jump Discontinuities: These occur when the function has a finite limit as x approaches a point from one side, but the limit is different when x approaches the point from the other side.
Infinite Discontinuities: These occur when the function approaches infinity or negative infinity as x approaches a point.

Asymptotes and Holes

Asymptotes are lines or curves that the function approaches as x approaches a certain value. Holes, on the other hand, are points where the function is not defined, but the limit of the function as x approaches that point exists.

Analyzing the Function

Let's analyze the function $f(x)=\frac{x+1}{6x^2-7x-3}$ and determine the nature of its discontinuities.

Finding the Roots of the Denominator

To find the roots of the denominator, we need to solve the equation $6x^2-7x-3=0$ . We can use the quadratic formula to find the roots:

$x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$

In this case, $a=6$ , $b=-7$ , and $c=-3$ . Plugging these values into the quadratic formula, we get:

$x=\frac{7\pm\sqrt{(-7)^2-4(6)(-3)}}{2(6)}$

$x=\frac{7\pm\sqrt{49+72}}{12}$

$x=\frac{7\pm\sqrt{121}}{12}$

$x=\frac{7\pm11}{12}$

Therefore, the roots of the denominator are $x=\frac{3}{2}$ and $x=-\frac{1}{3}$ .

Determining the Nature of the Discontinuities

Now that we have found the roots of the denominator, we need to determine the nature of the discontinuities at those points.

To do this, we can use the following steps:

Check if the function is defined at the point: If the function is not defined at the point, it is a discontinuity.
Check if the limit of the function as x approaches the point exists: If the limit exists, it is a removable discontinuity. If the limit does not exist, it is an infinite discontinuity.
Check if the function approaches infinity or negative infinity as x approaches the point: If the function approaches infinity or negative infinity, it is an infinite discontinuity.

Let's apply these steps to the function $f(x)=\frac{x+1}{6x^2-7x-3}$ and the points $x=\frac{3}{2}$ and $x=-\frac{1}{3}$ .

Discontinuity at $x=\frac{3}{2}$

At $x=\frac{3}{2}$ , the function is not defined because the denominator is equal to zero. Therefore, it is a discontinuity.

To determine the nature of the discontinuity, we need to check if the limit of the function as x approaches $\frac{3}{2}$ exists.

We can do this by factoring the numerator and denominator:

$f(x)=\frac{(x+1)(x-1)}{(x-\frac{3}{2})(2x+3)}$

Now, we can cancel out the common factors:

$f(x)=\frac{x-1}{2x+3}$

As x approaches $\frac{3}{2}$ , the numerator approaches $-1$ and the denominator approaches $9$ . Therefore, the limit of the function as x approaches $\frac{3}{2}$ exists, and it is equal to $-\frac{1}{9}$ .

Since the limit exists, it is a removable discontinuity.

Discontinuity at $x=-\frac{1}{3}$

At $x=-\frac{1}{3}$ , the function is not defined because the denominator is equal to zero. Therefore, it is a discontinuity.

To determine the nature of the discontinuity, we need to check if the limit of the function as x approaches $-\frac{1}{3}$ exists.

We can do this by factoring the numerator and denominator:

$f(x)=\frac{(x+1)(x-1)}{(x-\frac{3}{2})(2x+3)}$

Now, we can cancel out the common factors:

$f(x)=\frac{x-1}{2x+3}$

As x approaches $-\frac{1}{3}$ , the numerator approaches $-\frac{4}{3}$ and the denominator approaches $-7$ . Therefore, the limit of the function as x approaches $-\frac{1}{3}$ does not exist.

Since the limit does not exist, it is an infinite discontinuity.

Conclusion

In conclusion, the function $f(x)=\frac{x+1}{6x^2-7x-3}$ has a removable discontinuity at $x=\frac{3}{2}$ and an infinite discontinuity at $x=-\frac{1}{3}$ .

Therefore, the correct statement is:

A. There are asymptotes at $x=\frac{3}{2}$ and $x=-\frac{1}{3}$ .

This statement is true because the function has a removable discontinuity at $x=\frac{3}{2}$ , which is equivalent to an asymptote.

References

[1] Calculus: Early Transcendentals by James Stewart
[2] Algebra and Trigonometry by Michael Sullivan
[3] Precalculus: Functions and Graphs by David Cohen

Additional Resources

[1] Khan Academy: Discontinuities
[2] MIT OpenCourseWare: Calculus
[3] Wolfram Alpha: Discontinuities
Discontinuities of Rational Functions: A Comprehensive Analysis ===========================================================

Q&A: Discontinuities of Rational Functions

In this article, we will continue to explore the concept of discontinuities of rational functions. We will answer some frequently asked questions about discontinuities and provide additional examples to help solidify your understanding.

Q: What is a discontinuity in a rational function?

A: A discontinuity in a rational function occurs when the function is not defined at a particular point or when the function's graph has a gap or a break at that point.

Q: What are the different types of discontinuities?

A: There are three types of discontinuities:

Removable Discontinuities: These occur when the function is not defined at a point, but the limit of the function as x approaches that point exists.
Jump Discontinuities: These occur when the function has a finite limit as x approaches a point from one side, but the limit is different when x approaches the point from the other side.
Infinite Discontinuities: These occur when the function approaches infinity or negative infinity as x approaches a point.

Q: How do I determine the nature of a discontinuity?

A: To determine the nature of a discontinuity, you need to follow these steps:

Check if the function is defined at the point: If the function is not defined at the point, it is a discontinuity.
Check if the limit of the function as x approaches the point exists: If the limit exists, it is a removable discontinuity. If the limit does not exist, it is an infinite discontinuity.
Check if the function approaches infinity or negative infinity as x approaches the point: If the function approaches infinity or negative infinity, it is an infinite discontinuity.

Q: What is the difference between an asymptote and a discontinuity?

A: An asymptote is a line or curve that the function approaches as x approaches a certain value. A discontinuity, on the other hand, is a point where the function is not defined or has a gap or a break.

Q: Can a rational function have both asymptotes and discontinuities?

A: Yes, a rational function can have both asymptotes and discontinuities. For example, the function $f(x)=\frac{x+1}{6x^2-7x-3}$ has an asymptote at $x=\frac{3}{2}$ and a discontinuity at $x=-\frac{1}{3}$ .

Q: How do I find the roots of the denominator of a rational function?

A: To find the roots of the denominator of a rational function, you need to solve the equation $ax^2+bx+c=0$ , where $a$ , $b$ , and $c$ are the coefficients of the quadratic equation.

Q: What is the significance of the roots of the denominator?

A: The roots of the denominator are the points where the function is not defined. They are also the points where the function has a discontinuity.

Q: Can a rational function have a removable discontinuity?

A: Yes, a rational function can have a removable discontinuity. For example, the function $f(x)=\frac{x+1}{6x^2-7x-3}$ has a removable discontinuity at $x=\frac{3}{2}$ .

Q: How do I determine if a rational function has a removable discontinuity?

A: To determine if a rational function has a removable discontinuity, you need to follow these steps:

Check if the function is defined at the point: If the function is not defined at the point, it is a discontinuity.
Check if the limit of the function as x approaches the point exists: If the limit exists, it is a removable discontinuity.
Check if the function approaches infinity or negative infinity as x approaches the point: If the function approaches infinity or negative infinity, it is an infinite discontinuity.

Q: Can a rational function have a jump discontinuity?

A: Yes, a rational function can have a jump discontinuity. For example, the function $f(x)=\frac{x+1}{6x^2-7x-3}$ has a jump discontinuity at $x=-\frac{1}{3}$ .

Q: How do I determine if a rational function has a jump discontinuity?

A: To determine if a rational function has a jump discontinuity, you need to follow these steps:

Check if the function has a finite limit as x approaches the point from one side: If the limit exists, it is a removable discontinuity.
Check if the limit is different when x approaches the point from the other side: If the limit is different, it is a jump discontinuity.
Check if the function approaches infinity or negative infinity as x approaches the point: If the function approaches infinity or negative infinity, it is an infinite discontinuity.

Q: Can a rational function have an infinite discontinuity?

A: Yes, a rational function can have an infinite discontinuity. For example, the function $f(x)=\frac{x+1}{6x^2-7x-3}$ has an infinite discontinuity at $x=-\frac{1}{3}$ .

Q: How do I determine if a rational function has an infinite discontinuity?

A: To determine if a rational function has an infinite discontinuity, you need to follow these steps:

Check if the function approaches infinity or negative infinity as x approaches the point: If the function approaches infinity or negative infinity, it is an infinite discontinuity.
Check if the limit of the function as x approaches the point exists: If the limit exists, it is a removable discontinuity.
Check if the function has a finite limit as x approaches the point from one side: If the limit exists, it is a removable discontinuity.

Conclusion

In conclusion, discontinuities of rational functions are an important concept in mathematics. Understanding the different types of discontinuities and how to determine their nature is crucial for solving various mathematical problems. We hope that this article has provided you with a comprehensive understanding of discontinuities of rational functions and has helped you to better understand this important concept.

References

[1] Calculus: Early Transcendentals by James Stewart
[2] Algebra and Trigonometry by Michael Sullivan
[3] Precalculus: Functions and Graphs by David Cohen

Additional Resources

[1] Khan Academy: Discontinuities
[2] MIT OpenCourseWare: Calculus
[3] Wolfram Alpha: Discontinuities