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(a) find the inverse function of \(f\), (b) graph both \(f\) and \(f^{-1}\) on the same set of coordinate axes, (c) describe the relationship between the graphs of \(f\) and \(f^{-1}\), and (d) state the domain and range of \(f\) and \(f^{-1}\). $$ f(x)=\frac{6 x+4}{4 x+5} $$

Short Answer

Expert verified
Inverse function: \(f^-1(x) = \frac{4x-4}{6-x}\). The graph of \(f\) and its inverse \(f^-1\) are reflections of each other about the line \(y = x\). The domain for \(f\) is all real numbers except \(x = -\frac{5}{4}\) and for \(f^-1\) is all real numbers except \(x = 6\). The range for both \(f\) and \(f^-1\) is all real numbers, as both functions can yield any real number result.

Step by step solution

01

Finding the Inverse of the Function

To find the inverse of the function \(f(x) = \frac{6x+4}{4x+5}\), interchange \(x\) and \(y\) and solve for \(y\). This will yield: 1. Swap \(x\) and \(y\) to get \(x = \frac{6y+4}{4y+5}\) 2. Cross-multiply to get \(4xy + 5x = 6y + 4\) 3. Isolate \(y\) to get \(y = \frac{4x-4}{6-x}\). So, \(f^{-1}(x) = \frac{4x-4}{6-x}\).
02

Graphing the Function and Its Inverse

Start by graphing the original function \(f(x) = \frac{6x+4}{4x+5}\) and its inverse \(\frac{4x-4}{6-x}\) on the same set of coordinates. Ensure that the function and its inverse are reflections of each other about the line \(y = x\). This is because \(f(x) = y\) is equivalent to \(f^{-1}(y) = x\).
03

Describing the Relationship

The function \(f\) and its inverse \(f^{-1}\) are reflections of each other about the line \(y = x\). This is because converting a function into its inverse involves 'flipping' the graph over this line. Thus, the relationship between a function and its inverse is always based on this symmetry.
04

Stating the Domain and Range

For the original function \(f\), given \(f(x) = \frac{6x+4}{4x+5}\), the function is defined for all real numbers except \(x = -\frac{5}{4}\). Hence, the domain of \(f\) is all real numbers except \(x = -\frac{5}{4}\) and the range of \(f\) is all real numbers since the function can yield any real number result. For the inverse function \(f^{-1}\), given \(f^{-1}(x) = \frac{4x-4}{6-x}\), the function is defined for all real numbers except \(x = 6\). Hence, the domain of \(f^{-1}\) is all real numbers except \(x = 6\), and the range of \(f^{-1}\) is all real numbers as it can yield any real number result.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Graphing Inverse Functions
Understanding how to graph inverse functions starts with the basic premise that an inverse function, denoted as f-1(x), undoes whatever the original function f(x) does. Imagine you have a process, like turning the lights on. The inverse of that process is turning the lights off, which reverses the action. Likewise, f-1(x) reverses the action of f(x).

To graph f-1(x), you can use the coordinates of the original function f(x) and swap the x and y values. This means that a point on f(x) at (a, b) will appear on f-1(x) at (b, a). This swapping reflects each point over the line y = x, which is the essence of graphical representation for inverse functions.

For instance, in the given exercise, once you solve for the inverse algebraically, you plot the values for both f(x) and its inverse. Keep in mind that each function will have the other's points reflected over the line y = x, revealing a symmetry that confirms their inverse relationship.
Domain and Range of a Function
The domain of a function includes all the possible input values (usually represented by x) for which the function is defined, while the range includes all possible output values (usually represented by y). It's helpful to think of the domain as a machine's limitations on what sizes of materials it can accept, and the range as all the various products the machine can produce.

In the provided exercise, the domain of f(x) = \(\frac{6x+4}{4x+5}\) excludes the value x = -\(\frac{5}{4}\) to prevent division by zero, a mathematical impossibility. Conversely, its range is all real numbers since the outputs can cover the entire spectrum of real values. When we switch to the inverse function f-1(x), the domain and the range essentially switch places, with the new domain of f-1(x) being all real numbers except x = 6 for similar reasons related to division by zero, and the range covering all real numbers.
Reflection Across the Line y=x
Reflection across the line y = x is a neat trick to visually check if two functions are inverses of each other. Like a butterfly's wings or a human's left and right hands, a function and its inverse will mirror each other across this line.

In practical terms, for every point (x, y) on graph f(x), there exists a corresponding point (y, x) on graph f-1(x). The line y = x acts as the mirror. So, if you fold the graph along this line, the function and its inverse should overlap perfectly.

To apply this concept in exercises such as the one provided, you can draw or imagine the line y = x on your graph and envision flipping the graph of the original function over it. If you plotted both correctly, you'll see that the function and its inverse will match up exactly on opposite sides of the line. This visual check not only helps confirm your algebraic work but also strengthens your understanding of the way that functions and inverses relate to one another.

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Most popular questions from this chapter

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The lengths (in feet) of the winning men's discus throws in the Olympics from 1920 through 2008 are listed below. (Source: International Olympic Committee) $$\begin{array}{llllll} 1920 & 146.6 & 1956 & 184.9 & 1984 & 218.5 \\ 1924 & 151.3 & 1960 & 194.2 & 1988 & 225.8 \\ 1928 & 155.3 & 1964 & 200.1 & 1992 & 213.7 \\ 1932 & 162.3 & 1968 & 212.5 & 1996 & 227.7 \\ 1936 & 165.6 & 1972 & 211.3 & 2000 & 227.3 \\ 1948 & 173.2 & 1976 & 221.5 & 2004 & 229.3 \\ 1952 & 180.5 & 1980 & 218.7 & 2008 & 225.8 \end{array}$$ (a) Sketch a scatter plot of the data. Let \(y\) represent the length of the winning discus throw (in feet) and let \(t=20\) represent 1920 (b) Use a straightedge to sketch the best-fitting line through the points and find an equation of the line. (c) Use the regression feature of a graphing utility to find the least squares regression line that fits the data. (d) Compare the linear model you found in part (b) with the linear model given by the graphing utility in part (c). (e) Use the models from parts (b) and (c) to estimate the winning men's discus throw in the year 2012 .

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