Chapter 4: Problem 293
Graph the function on a graphing calculator on the window \(x=[-5,5]\) and estimate the horizontal asymptote or limit. Then, calculate the actual horizontal asymptote or limit. \(\lim _{x \rightarrow \infty} \frac{3 x+2}{x+5}\)
Short Answer
Expert verified
The horizontal asymptote of \( \frac{3x+2}{x+5} \) is \( y=3 \).
Step by step solution
01
Understanding the Function
The given function is \( f(x) = \frac{3x + 2}{x + 5} \). Here, we are asked to graph this function using a graphing calculator and find the horizontal asymptote by estimating and calculating it.
02
Graph the Function
Using a graphing calculator, plot the function \( f(x) = \frac{3x + 2}{x + 5} \) with the window setting for \( x \) from -5 to 5. Identify the horizontal direction in which the function seems to approach a constant value.
03
Estimate the Horizontal Asymptote
Observe the graph you produced. As \( x \) approaches both positive and large values, the function approaches a particular y-value. Estimate what this y-value appears to be from the graph.
04
Set Up the Limit Calculation
The formal way to find the horizontal asymptote is through limit calculation: \( \lim_{{x \to \infty}} \frac{3x + 2}{x + 5} \). Factoring \( x \) out from the numerator and the denominator gives \( \frac{3 + \frac{2}{x}}{1 + \frac{5}{x}} \).
05
Apply Limit Properties
As \( x \) approaches infinity, the terms \( \frac{2}{x} \) and \( \frac{5}{x} \) both approach 0. Thus, the expression simplifies to \( \frac{3 + 0}{1 + 0} = 3 \).
06
Conclude Horizontal Asymptote
Hence, \( \, \lim_{{x \to \infty}} \frac{3x + 2}{x + 5} = 3 \). The horizontal asymptote is the line \( y = 3 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Graphing Calculator
A graphing calculator is a powerful tool that helps visualize mathematical functions. For this exercise, it is used to graph the function \( f(x) = \frac{3x + 2}{x + 5} \) over the window \( x = [-5, 5] \). When using a graphing calculator, follow these basic steps:
- Enter the function into the calculator's function editor.
- Set the viewing window from \( x = -5 \) to \( x = 5 \), which lets you see how the function behaves in this region.
- Plot the graph to observe the curve as it moves towards larger x-values.
Limit Calculation
The concept of a limit is fundamental to understanding horizontal asymptotes. For the function \( f(x) = \frac{3x + 2}{x + 5} \), you want to determine its behavior as \( x \) approaches infinity. To calculate the limit, start by expressing it as:\[ \lim_{x \to \infty} \frac{3x + 2}{x + 5} \]Breaking down this expression helps you understand how the function behaves over large values of \( x \).Substitute terms in the numerator and the denominator to factor out \( x \):\[ \frac{3 + \frac{2}{x}}{1 + \frac{5}{x}} \]Notice that as \( x \) increases, \( \frac{2}{x} \) and \( \frac{5}{x} \) approach zero. This simplification gives the limit as 3.
Infinite Limit
An infinite limit refers to the behavior of a function as the input grows indefinitely large. In this context, we're looking at what happens to \( f(x) = \frac{3x + 2}{x + 5} \) as \( x \to \infty \). For rational functions such as this one, the highest degree terms in the numerator and denominator dictate the limit.By simplifying \( \frac{3x + 2}{x + 5} \) to \( \frac{3}{1} \) as \( x \to \infty \), you can see that the infinite limit results in the value 3. This calculation not only finds the limit but also confirms the horizontal asymptote at \( y = 3 \), indicating that the function approaches this y-value.
Rational Functions
Rational functions are quotients of polynomial expressions. In our case, the function \( f(x) = \frac{3x + 2}{x + 5} \) is a simple example. You can express the behavior of such functions through their limits and asymptotes.Important properties of rational functions include:
- Vertical asymptotes occur where the denominator is zero.
- Horizontal asymptotes are determined by the degrees of the numerator and denominator polynomials.