Chapter 11: Problem 51
Each of the following functions is one-to-one. Find the inverse of each function and express it using \(f^{-1}(x)\) notation. \(f(x)=2 x^{3}-3\)
Short Answer
Expert verified
The inverse of the function is \( f^{-1}(x) = \sqrt[3]{\frac{x + 3}{2}} \).
Step by step solution
01
Understand the Function
We are given the function \( f(x) = 2x^3 - 3 \). Our goal is to find its inverse, which we will denote as \( f^{-1}(x) \).
02
Replace Function Notation with Output Variable
Replace \( f(x) \) with \( y \), so the function becomes \( y = 2x^3 - 3 \).
03
Swap Variables
To find the inverse, swap \( x \) and \( y \). The equation becomes \( x = 2y^3 - 3 \).
04
Solve for the Original Input Variable
Solve the equation for \( y \):1. Add 3 to both sides: \( x + 3 = 2y^3 \).2. Divide both sides by 2: \( \frac{x + 3}{2} = y^3 \).3. Take the cube root of both sides: \( y = \sqrt[3]{\frac{x + 3}{2}} \).
05
Write the Inverse Function
The inverse function is therefore \( f^{-1}(x) = \sqrt[3]{\frac{x + 3}{2}} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
One-to-One Functions
A one-to-one function is a special type of function where each input corresponds to a unique output. This means that no two different inputs will produce the same output. One way to check if a function is one-to-one is by using the horizontal line test. For this test, you draw horizontal lines across the graph of the function.
- If any horizontal line intersects the graph more than once, the function is not one-to-one.
- If no horizontal line intersects the graph more than once, the function is one-to-one.
Function Notation
Function notation is a concise way of expressing the idea of a function. It uses symbols to convey the action of a function on an input to produce an output. In the notation \( f(x) \), \( f \) is the name of the function, and \( x \) is the input variable. The output of the function is usually expressed as a mathematical rule applied to \( x \).
In the context of finding an inverse, we first express \( f \) in terms of \( y \) (the output). For example, \( y = 2x^3 - 3 \). This expression helps when swapping \( x \) and \( y \) to find the inverse.
In the context of finding an inverse, we first express \( f \) in terms of \( y \) (the output). For example, \( y = 2x^3 - 3 \). This expression helps when swapping \( x \) and \( y \) to find the inverse.
- Remember: Inverse functions are denoted using \( f^{-1}(x) \).
- Function notation aids in clearly distinguishing between a function and its inverse.
Cube Root
A cube root is the number that, when multiplied by itself three times, gives the original number. The cube root symbol \( \sqrt[3]{} \) is used to denote this operation.
For example, the cube root of 8 is 2, since \( 2 \times 2 \times 2 = 8 \). Calculating the cube root is essential when solving for an inverse function, especially if the function involves a cube, as demonstrated in the function \( x = 2y^3 - 3 \).
The step requires taking the cube root of both sides to isolate \( y \), resulting in \( y = \sqrt[3]{\frac{x + 3}{2}} \). This move is a crucial part of solving and manipulating equations involving cubes.
For example, the cube root of 8 is 2, since \( 2 \times 2 \times 2 = 8 \). Calculating the cube root is essential when solving for an inverse function, especially if the function involves a cube, as demonstrated in the function \( x = 2y^3 - 3 \).
The step requires taking the cube root of both sides to isolate \( y \), resulting in \( y = \sqrt[3]{\frac{x + 3}{2}} \). This move is a crucial part of solving and manipulating equations involving cubes.
Solving Equations
Solving equations involves manipulating expressions to find the value of a variable. It often includes steps like isolating variables, adding or subtracting terms, and applying operations like division or taking roots.
In the exercise, we solve for \( y \) after swapping \( x \) and \( y \) in the equation \( x = 2y^3 - 3 \). This requires:
In the exercise, we solve for \( y \) after swapping \( x \) and \( y \) in the equation \( x = 2y^3 - 3 \). This requires:
- Adding 3 to both sides to simplify: \( x + 3 = 2y^3 \).
- Dividing both sides by 2 to continue isolating \( y \): \( \frac{x + 3}{2} = y^3 \).
- Taking the cube root of both sides to find \( y \), resulting in \( y = \sqrt[3]{\frac{x + 3}{2}} \).