Chapter 3: Problem 465
For the following exercises, find the domain, vertical asymptotes, and horizontal asymptotes of the functions. $$f(x)=\frac{2}{5 x+2}$$
Short Answer
Expert verified
Domain: \((-\infty, -\frac{2}{5}) \cup (-\frac{2}{5}, \infty)\); Vertical asymptote: \(x = -\frac{2}{5}\); Horizontal asymptote: \(y = 0\).
Step by step solution
01
Find the Domain
The domain of a function is the set of all possible input values (x-values) that will not produce division by zero or any undefined expressions. For the function \( f(x) = \frac{2}{5x + 2} \), the denominator is \( 5x + 2 \). Set this equal to zero to find the restricted values: \[ 5x + 2 = 0 \]Solve for \( x \):\[ 5x = -2 \]\[ x = -\frac{2}{5} \]Thus, the domain is all real numbers except \( x = -\frac{2}{5} \) or in interval notation, \( (-\infty, -\frac{2}{5}) \cup (-\frac{2}{5}, \infty) \).
02
Find the Vertical Asymptotes
Vertical asymptotes occur at values of \( x \) where the function tends toward infinity, often when the denominator is zero. From Step 1, we determined that the denominator \( 5x + 2 = 0 \) at \( x = -\frac{2}{5} \). Therefore, there is a vertical asymptote at \( x = -\frac{2}{5} \).
03
Find the Horizontal Asymptotes
Horizontal asymptotes are found by analyzing the behavior of the function as \( x \) approaches infinity. For a rational function \( \frac{a}{bx+c} \), the horizontal asymptote is at \( y = 0 \) if the degree of the polynomial in the denominator is greater than the degree of the numerator:- The degree of the numerator \( 2 \) is 0 since it's a constant function.- The degree of the denominator \( 5x + 2 \) is 1 since it's a linear expression.Since the degree of the denominator is greater, \( f(x) \) approaches 0 as \( x \to \pm \infty \). Thus, the horizontal asymptote is \( y = 0 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Rational Functions
A rational function is a ratio of two polynomials, where the numerator and the denominator are polynomial expressions. In our exercise, the function given is \[ f(x) = \frac{2}{5x + 2} \]Here:
- The numerator is "2", a constant term, which is a polynomial of degree 0.
- The denominator is "5x + 2", a linear polynomial of degree 1.
Vertical Asymptotes
Vertical asymptotes are lines that the graph of the function approaches but never touches. They occur at the x-values where the denominator equals zero, as the function tends toward infinity or negative infinity at these points. Let’s recall our equation: \[ f(x)=\frac{2}{5x+2} \]
- To find where the vertical asymptotes are, we set the denominator equal to zero because division by zero is undefined.
- For \( 5x + 2 = 0 \), solve for \( x \): \[ 5x = -2 \] \[ x = -\frac{2}{5} \]
Horizontal Asymptotes
Horizontal asymptotes describe the behavior of a function as the input \( x \) becomes very large or very small, approaching infinity. They indicate the line which the function values approach but may never reach.To analyze these for our rational function \( f(x) = \frac{2}{5x + 2} \), we compare the degrees of the numerator and denominator:
- The degree of the numerator (2) is 0, because it's a constant.
- The degree of the denominator (5x + 2) is 1, making it a linear expression.
Function Analysis
Analyzing a function like \( f(x)=\frac{2}{5x+2} \) involves understanding its behavior across all x-values. This includes determining where the function is defined, the intervals where it is increasing or decreasing, and how it behaves near its asymptotes:
- The domain is all real numbers except \( x = -\frac{2}{5} \), due to the zero in the denominator.
- The vertical asymptote at \( x = -\frac{2}{5} \) suggests that the function will approach positive or negative infinity there, without ever actually taking a value.
- Because there is a horizontal asymptote at \( y = 0 \), as \( x \) grows very large or very small, the output values will inch towards zero.