Chapter 10: Problem 46
Find all asymptotes, \(x\) -intercepts, and \(y\) -intercepts for the graph of each rational function and sketch the graph of the function. $$f(x)=\frac{2 x^{2}+1}{x^{3}-x}$$
Short Answer
Expert verified
Vertical asymptotes at \(x = 0\), \(x = 1\), and \(x = -1\). Horizontal asymptote at \(y = 0\). No \(x\)-intercepts and no \(y\)-intercepts.
Step by step solution
01
- Identify Vertical Asymptotes
Find the vertical asymptotes by setting the denominator equal to zero. The denominator of the function is \(x^3 - x\). Set it to zero and solve for \(x\):\[x^3 - x = 0\]Factoring this gives:\[x(x^2 - 1) = 0\]Further factorization gives:\[x(x - 1)(x + 1) = 0\]The solutions are \(x = 0\), \(x = 1\), and \(x = -1\).These are the vertical asymptotes.
02
- Identify Horizontal Asymptotes
Determine the horizontal asymptotes by comparing the degrees of the numerator and the denominator. The degrees are compared as follows:- The degree of the numerator \(2x^2 + 1\) is 2.- The degree of the denominator \(x^3 - x\) is 3.Since the degree of the numerator is less than the degree of the denominator, the horizontal asymptote is at \(y = 0\).
03
- Find the x-intercepts
Find the \(x\)-intercepts by setting the numerator equal to zero. The numerator of the function is \(2x^2 + 1\). Set it to zero and solve for \(x\):\[2x^2 + 1 = 0\]Solving this equation:\[2x^2 = -1\]Since this equation has no real solution, the function has no \(x\)-intercepts.
04
- Find the y-intercepts
Find the \(y\)-intercepts by evaluating the function at \(x = 0\):\[f(0) = \frac{2(0)^2 + 1}{(0)^3 - 0} = \frac{1}{0}\]Since the function evaluates to an undefined value, there is no \(y\)-intercept.
05
- Sketch the graph
Consider all information obtained:- Vertical asymptotes at \(x = 0\), \(x = 1\), and \(x = -1\).- Horizontal asymptote at \(y = 0\).- No \(x\)-intercepts and no \(y\)-intercepts.Using this information, sketch the graph of the function showing the behavior approaching the asymptotes.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
vertical asymptotes
Vertical asymptotes occur where the denominator of a rational function equals zero and makes the function undefined. To find vertical asymptotes, we need to factor the denominator and solve for when it equals zero. Given the function $$f(x) = \frac{2x^2 + 1}{x^3 - x}$$First, set the denominator equal to zero:$$x^3 - x = 0$$We factor this to$$x(x^2 - 1) = 0$$and further to$$x(x - 1)(x + 1) = 0$$This gives solutions at$$x = 0$$,$$x = 1$$, and$$x = -1$$. Each of these solutions corresponds to a vertical asymptote. Therefore, the vertical asymptotes are at $$x = 0$$,$$x = 1$$,and $$x = -1$$.
horizontal asymptotes
Horizontal asymptotes are determined by comparing the degrees of the numerator and denominator in a rational function. To find horizontal asymptotes: 1. Note the degrees of the numerator and the denominator. 2. Compare these degrees to determine the appropriate rule.For the function $$f(x) = \frac{2x^2 + 1}{x^3 - x}$$, the degree of the numerator $$2x^2 + 1$$ is 2,and the degree of the denominator $$x^3 - x$$ is 3. Since the degree of the numerator (2) is less than the degree of the denominator (3), the horizontal asymptote is at $$y = 0$$. When the degree of the numerator is smaller, the horizontal asymptote will always be at$$y = 0$$.
intercepts in functions
Intercepts are the points where the function crosses the axes. There are two types: x-intercepts and y-intercepts.**x-Intercepts**: These occur where the numerator of the rational function equals zero, provided the denominator does not equal zero.Given the function $$f(x) = \frac{2x^2 + 1}{x^3 - x}$$,we set the numerator to zero:$$2x^2 + 1 = 0$$This gives$$2x^2 = -1$$, but you will notice that a negative number cannot equal a square result for real numbers. Therefore, there are no real x-intercepts for this function.**y-Intercepts**: These occur where the function crosses the y-axis. To find it, evaluate the function at $$x = 0$$:$$f(0) = \frac{2(0)^2 + 1}{(0)^3 - 0} = \frac{1}{0}$$The value is undefined, so there is no y-intercept for this function.
rational functions
Rational functions are expressions of the form$$\frac{P(x)}{Q(x)}$$,where both$$P(x)$$ and$$Q(x)$$ are polynomials. For more complex rational functions like $$f(x) = \frac{2x^2 + 1}{x^3 - x}$$, key characteristics include: - **Asymptotes**: These are found where the function's denominator equals zero (vertical) and by comparing degrees of the numerator and denominator (horizontal). - **Intercepts**: Determine where the function intersects the x-axis and y-axis.Understanding these key features of rational functions helps in sketching their graphs and analyzing their behavior.
graphing functions
Graphing functions like $$f(x) = \frac{2x^2 + 1}{x^3 - x}$$ requires understanding its key features:1. **Vertical Asymptotes**: Found at $$x = 0$$,$$x = 1$$,and $$x = -1$$. These lines illustrate where the graph approaches but never touches.2. **Horizontal Asymptote**: Found at $$y = 0$$,and it shows the behavior of the function as $$x \to \text{infinity or -infinity}$$.3. **Intercepts**: In this function, there are no x-intercepts or y-intercepts.To sketch, plot the asymptotes first. Then, consider the behavior of the function near these asymptotes and the origin. Use additional points for more precision, but recognizing asymptotes and intercepts will give a strong initial outline.