Question

Compare the graph of \(f(x)=1 / x\) with the graph of \(g\). $$g(x)=-f(x)=-\frac{1}{x}$$

Short answer

The graph of \(g(x)=-f(x)=-\frac{1}{x}\) is a reflection of the graph of \(f(x)=\frac{1}{x}\) about the x-axis. This results in the graphs being identical except for the locations of their branches; the graph of \(f(x)\) has branches in the first and third quadrants while that of \(g(x)\) has branches in the second and fourth quadrants.

Step-by-step solution

Understanding the Graph of f(x)

The function \(f(x)=\frac{1}{x}\) is a hyperbola that has two branches located in the first and third quadrants (for positive and negative x, respectively). It is symmetrical about the origin. The graph approaches but never reaches the x and y axis, implying it has vertical and horizontal asymptotes at x=0 and y=0.

Reflecting f(x) about the x-axis

The graph of \(g(x)=-f(x)=-\frac{1}{x}\) is a reflection of \(f(x)\) about the x-axis. This is simply flipping the graph of \(f(x)\) upside down, which results in the branches located in the second and fourth quadrants (for negative and positive x, respectively). It also has vertical and horizontal asymptotes at x=0 and y=0.

Comparison of f(x) and g(x)

The graph of \(f(x)\) has branches in the first and third quadrants while the graph of \(g(x)\) is the reflection of \(f(x)\) and thus has branches in the second and fourth quadrants. The two graphs are the same in all respects except for their location. Both functions are undefined at x=0 due to their vertical asymptotes.

Key concepts

Hyperbola Graphs

A hyperbola is a type of conic section that appears frequently in algebra and calculus. The graph of a hyperbola has two separate branches that curve away from each other. These branches are the hallmark of a hyperbolic function, and they are distinctive because they never meet no matter how far they extend in their respective directions.

For the function given by the equation, \(f(x) = \frac{1}{x}\), we have what is known as a rectangular hyperbola. Its branches are located in the first and third quadrants for positive and negative values of \(x\), respectively. One key feature to note is that as the value of \(x\) becomes larger, the value of \(f(x)\) approaches zero, and when \(x\) approaches zero, \(f(x)\) becomes infinitely large in magnitude. These characteristics contribute to the creation of its two asymptotes.

Reflection Across the X-Axis

Reflections in mathematics often involve 'flipping' or 'mirroring' a graph over a specific line, which could be either the x-axis or y-axis. When reflecting a graph across the x-axis, every point on the graph has its \(y\)-coordinate multiplied by -1 while the \(x\)-coordinate remains the same. This transformation changes the sign of the output values for a function without altering the input.

In the case of the function \(g(x) = -f(x) = -\frac{1}{x}\), we see that the entire graph of \(f(x)\) is flipped upside down. This creates a visual effect as if the graph has been 'pressed' onto the x-axis, creating a mirror image. Following this reflection, the new branches of the hyperbola \(g(x)\) are now located in the second and fourth quadrants.

Vertical and Horizontal Asymptotes

Asymptotes are important features in the study of graphs; they are lines that a graph approaches but never actually touches or crosses. Hyperbolas typically have two types of asymptotes—vertical and horizontal. A vertical asymptote is a vertical line that a function approaches but does not intersect, often leading to undefined points. It indicates where a function is discontinuous and represents values for which the function heads towards infinity.

The function \(f(x)\) has a vertical asymptote at \(x=0\) and a horizontal asymptote at \(y=0\), representing values the graph approaches but will never reach. The presence of these asymptotes is central to understanding the behavior of the hyperbola, especially near points of undefined value such as \(x=0\) in this instance.

Undefined Points in Functions

In mathematics, we encounter functions that have points where they are not defined. These 'undefined points' typically arise due to division by zero or because the result of a function is not a real number. Points of discontinuity can significantly impact the shape and properties of a function's graph.

The hyperbolic functions \(f(x)\) and \(g(x)\) both have a point of discontinuity at \(x=0\), which is also the location of their vertical asymptote. At this value, the functions become undefined because division by zero is not possible in the realm of real numbers. When graphing, this discontinuity translates into a 'gap' where the function does not exist, and the branches of the hyperbola will curve around but never cross this vertical line.