Chapter 1: Problem 190
For the following exercises, a. find the inverse function, and b. find the domain and range of the inverse function. $$ f(x)=\sqrt[3]{x-4} $$
Short Answer
Expert verified
The inverse is \( f^{-1}(x) = x^3 + 4 \). The domain and range are both \(-\infty, \infty\).
Step by step solution
01
Set up the equation for the inverse function
To find the inverse function, we start by considering the equation given: \[ f(x) = \sqrt[3]{x-4} \]We need to express \( f(x) \) in terms of \( y \):\[ y = \sqrt[3]{x-4} \]
02
Solve for x in terms of y
We will manipulate the equation to express \( x \) in terms of \( y \). Start by eliminating the cube root on the right side of the equation:\[ y^3 = x - 4 \]Next, solve for \( x \) by adding 4 to both sides:\[ x = y^3 + 4 \]
03
Express the inverse function
Now that we have \( x \) in terms of \( y \), interchange \( x \) and \( y \) to express the inverse function. Replace \( y \) with \( f^{-1}(x) \) and \( x \) with \( y \) in the equation:\[ f^{-1}(x) = x^3 + 4 \]
04
Determine the domain of the inverse function
The domain of the inverse function \( f^{-1}(x) = x^3 + 4 \) is all real numbers because any real number \( x \) can be cubed and then added to 4. Therefore, the domain is:\(-\infty, \infty\)
05
Determine the range of the inverse function
The range of the inverse function is also all real numbers. Since a cubic function can take any real number as input and produce any real number as output, the range is:\(-\infty, \infty\)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Cubic Function
Cubic functions are a special type of polynomial function where the highest degree is three. This means the function will have the form \( ax^3 + bx^2 + cx + d \), where \( a, b, c, \) and \( d \) are constants, and \( a eq 0 \). In the context of our exercise, when finding the inverse, we specifically dealt with the function \( f(x) = \sqrt[3]{x-4} \). After manipulation, this function is transformed to \( f^{-1}(x) = x^3 + 4 \).
Key characteristics of cubic functions include:
Key characteristics of cubic functions include:
- They have one inflection point, where the curve changes concavity.
- The graph can cross the x-axis up to three times, depending on its roots.
- Cubic functions extend infinitely in both vertical directions as \( x \) becomes infinitely large or small.
Domain and Range
When analyzing functions, the domain represents all the possible inputs (\( x \)-values), while the range represents all possible outputs (\( y \)-values). In this exercise, we worked with inverse functions. After finding the inverse function \( f^{-1}(x) = x^3 + 4 \), it is crucial to determine its domain and range.
- The domain of \( f^{-1}(x) \) is all real numbers. Since you can potentially cube any real number and add four, there are no restrictions on \( x \).
- The range of \( f^{-1}(x) \) is also all real numbers. A cubic function can indeed reach any positive or negative value as output, reflecting symmetry and behavior on the graph.
Function Manipulation
Function manipulation is a key skill in solving problems involving inverse functions. It involves changing the function’s equation to uncover new relationships or solve for variables.
In the exercise, we transformed \( f(x) = \sqrt[3]{x-4} \) into its inverse \( f^{-1}(x) = x^3 + 4 \). This required:
In the exercise, we transformed \( f(x) = \sqrt[3]{x-4} \) into its inverse \( f^{-1}(x) = x^3 + 4 \). This required:
- Eliminating operations: Start by removing the original cube root by cubing both sides of the equation, isolating the term inside the root.
- Solving for the variable: Rearrange terms to solve for the variable originally inside the root, ensuring that you're expressing it in terms of the new variable.
- Interchanging variables: Finally, swap the roles of x and y to derive the inverse, aligning with the functions’ symbolic expressions.