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In Exercises 1-8, find the inverse function of \(f\) informally. Verify that \(f\left(f^{-1}(x)\right)=x\) and \(f^{-1}(f(x))=x\). $$ f(x)=\frac{1}{3} x $$

Short Answer

Expert verified
The inverse function of \(f(x) = \frac{1}{3} x\) is \(f^{-1}(x) = 3x\). Verifying shows that \(f(f^{-1}(x)) = x\) and \(f^{-1}(f(x)) = x\).

Step by step solution

01

Interchange the roles of \(x\) and \(y\)

Write \(f(x)= \frac{1}{3}x\) as \(y=\frac{1}{3}x\). Then, interchange \(x\) and \(y\). This gives \(x=\frac{1}{3}y\).
02

Solve for \(y\)

To find \(y\), multiply both sides of the equation by 3. This gives \(y=3x\). This is the inverse function, denoted \(f^{-1}(x)\).
03

Verify \(f\left(f^{-1}(x)\right)=x\)

Substitute \(f^{-1}(x)\) into \(f(x)\). This gives \(f\left(f^{-1}(x)\right)=\frac{1}{3}\cdot (3x) = x\). This verifies that \(f\left(f^{-1}(x)\right) = x\).
04

Verify \(f^{-1}(f(x))=x\)

Substitute \(f(x)\) into \(f^{-1}(x)\). This gives \(f^{-1}\left(f(x)\)\right)=3 \cdot (\frac{1}{3}x) = x. This verifies that \(f^{-1}(f(x)) = x\).

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Key Concepts

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

Verifying Inverse Functions
When dealing with inverse functions, it's essential to understand that an inverse function reverses the operation of the original function. To verify that two functions are inverses of each other, we need to show that applying the inverse function after the original function—or vice versa—yields the identity result, effectively 'undoing' the function.

For the function given, \(f(x) = \frac{1}{3}x\), the verification process involves two critical evaluations: \(f(f^{-1}(x))\) and \(f^{-1}(f(x))\). If both expressions simplify to \(x\), then \(f^{-1}(x)\) is indeed the inverse of \(f(x)\). This concept is akin to confirming that a lock and key pair: if the key can lock and unlock seamlessly, it's the right match.
Finding Inverse Functions
The process of finding an inverse function can be thought of as flipping the function over a line. Algebraically, we switch the roles of the variables \(x\) and \(y\), then solve the resulting equation to get \(y\) by itself. This new \(y\) represents the inverse function, \(f^{-1}(x)\).

In the example of \(f(x) = \frac{1}{3}x\), after swapping \(x\) and \(y\), we solve \(x = \frac{1}{3}y\) for \(y\), multiplying both sides by 3 to obtain \(y = 3x\), which is the inverse, \(f^{-1}(x)\). This process is crucial as it provides a step-by-step method to uncover the inverse function from any given function, as long as the inverse exists.
Function Operations
Understanding function operations is foundational when working with functions in algebra. These operations include adding, subtracting, multiplying, dividing, and composing functions. With inverse functions, composition plays a central role, as it involves applying one function to the result of another.

In mathematical terms, the composition of \(f\) and its inverse \(f^{-1}\) is expressed as \(f(f^{-1}(x))\) and \(f^{-1}(f(x))\). Successfully executing these operations confirms the correctness of the inverse because they must return the input \(x\). These operations underscore the deep interconnectedness between functions and provide insight into how one function can modify the effects of another.
Algebraic Methods in Trigonometry
Algebraic methods in trigonometry are a cornerstone of mathematics, providing essential tools to work with trigonometric functions and their inverses. While the exercise provided doesn't involve trigonometry explicitly, it's worthwhile to mention that similar inverse operations and verification processes apply to trigonometric functions such as sine, cosine, and tangent.

Just as with linear functions, finding the inverse of a trigonometric function involves algebraically manipulating the equation to solve for the angle given the function value. Verification, too, follows the same principle where the composition of the function and its inverse should yield the original input. These algebraic methods apply universally across mathematical functions, making them a crucial area of study for students to master.

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Most popular questions from this chapter

True or False? In Exercises 85 and 86, determine whether the statement is true or false. Justify your answer. $$ \text { If } f \text { is an even function, } f^{-1} \text { exists. } $$

Find the average rate of change of the function from \(x_{1}\) to \(x_{2}\). $$ \begin{array}{cc} \text { Function } & x \text {-Values } \\ \(f(x)=x^{2}-2 x+8 &\quad x_{1}=1, x_{2}=5\) \end{array} $$

College Students The numbers of foreign students \(F\) (in thousands) enrolled in colleges in the United States from 1992 to 2002 can be approximated by the model. $$ F=0.004 t^{4}+0.46 t^{2}+431.6, \quad 2 \leq t \leq 12 $$ where \(t\) represents the year, with \(t=2\) corresponding to 1992. (Source: Institute of International Education) (a) Use a graphing utility to graph the model. (b) Find the average rate of change of the model from 1992 to 2002. Interpret your answer in the context of the problem. (c) Find the five-year time periods when the rate of change was the greatest and the least.

In Exercises 39-54, (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 \(f^{-1}\). $$ f(x)=x^{3}+1 $$

Your wage is \(\$ 8.00\) per hour plus \(\$ 0.75\) for each unit produced per hour. So, your hourly wage \(y\) in terms of the number of units produced is $$ y=8+0.75 x $$ (a) Find the inverse function. (b) What does each variable represent in the inverse function? (c) Determine the number of units produced when your hourly wage is \(\$ 22.25\).

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