Chapter 3: Problem 38
In Exercises \(37-40\), use a graphing utility to graph the function and identify any horizontal asymptotes. $$ f(x)=\frac{|3 x+2|}{x-2} $$
Short Answer
Expert verified
The function \(f(x)=\frac{|3x+2|}{x-2}\) has two horizontal asymptotes, \(y=3\) and \(y=-3\), and a vertical asymptote at \(x=2\).
Step by step solution
01
Deal with absolute value
The absolute value can be defined as \(|x| = x\) for \(x \geq 0\) and \(|x| = -x\) for \(x < 0\). Thus the function can be divided into two parts: \(f_1(x) = \frac{3x+2}{x-2}\) for \(3x+2 \geq 0\) and \(f_2(x) = \frac{-3x-2}{x-2}\) for \(3x+2 < 0\).
02
Find asymptotes
To find the horizontal asymptotes of the function, we examine the limit of the function as \(x \to \infty\) and \(x \to -\infty\). For \(f_1(x) = \frac{3x+2}{x-2}\), as \(x \to \infty\), \(f_1(x) \to 3\), and as \(x \to -\infty\), \(f_1(x) \to 3\). So \(y=3\) is a horizontal asymptote. As for \(f_2(x) = \frac{-3x-2}{x-2}\), as \(x \to \infty\), \(f_2(x) \to -3\), and as \(x \to -\infty\), \(f_2(x) \to -3\). So \(y=-3\) is a horizontal asymptote. Note that a vertical asymptote happens where the denominator of our function equals zero. So for \(x=2\) there's a vertical asymptote.
03
Graph the function
Now, plot the function \(f_1(x) = \frac{3x+2}{x-2}\) for \(3x+2 \geq 0\) and \(f_2(x) = \frac{-3x-2}{x-2}\) for \(3x+2 < 0\) to double check the calculated values. A graphing utility such as a graphic calculator or a computer program like GeoGebra can be used for this task.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Absolute Value Functions
An absolute value function involves expressions like \(|x|\), which measure the distance of a number from zero on the number line. It's always positive or zero, making it quite different from regular functions that can have negative outputs. Absolute value can be determined by:
- \(|x| = x\) for \(x \geq 0\)
- \(|x| = -x\) for \(x < 0\)
Limits at Infinity
Limits at infinity are used to understand the behavior of a function as the input value grows very large positively or negatively. For rational functions like \(f(x) = \frac{3x+2}{x-2}\), we focus on the highest power of \(x\) in the numerator and denominator to determine these limits.
- As \(x \to \infty\), \(f(x) \sim \frac{3x}{x} = 3\)
- As \(x \to -\infty\), \(f(x) \sim \frac{-3x}{x} = -3\)
Vertical Asymptotes
Vertical asymptotes occur where the denominator of a function equals zero, causing the function to become undefined, often leading to a graph rising or falling sharply. For our function \(f(x) = \frac{|3x+2|}{x-2}\), the denominator \(x-2\) equals zero when \(x=2\). When this happens, neither \(f_1(x)\) nor \(f_2(x)\) is defined because you can't divide by zero. Thus, \(x=2\) is a vertical asymptote, and the graph will show a sharp discontinuity at this point, meaning the function rises or falls towards infinity as it approaches \(x=2\) from either side. Recognizing vertical asymptotes is vital for sketching the accurate graph of a function.
Graphing Rational Functions
Graphing rational functions like \(f(x) = \frac{|3x+2|}{x-2}\) requires an understanding of both horizontal and vertical asymptotes, along with considering absolute values that influence the graph's behavior. When graphing, it’s essential to:
- Identify any asymptotes: both horizontal \(y=3\) and \(y=-3\), and the vertical \(x=2\).
- Determine the intervals for absolute values and split the function into parts.
- Use a graphing utility to accurately draw the curve and visualize behavior near asymptotes.