Chapter 4: Problem 36
Find the inverse function of \(f.\) \(f(x)=-x^{3}+2\)
Short Answer
Expert verified
The inverse function is \( f^{-1}(x) = \sqrt[3]{2 - x} \).
Step by step solution
01
Set the function equal to y
First, we represent the function as an equation in terms of y. Replace \( f(x) \) with \( y \): \[ y = -x^3 + 2 \]
02
Solve for x in terms of y
To find the inverse function, we need to express \( x \) in terms of \( y \). Start by isolating the term with \( x \): \[ y - 2 = -x^3 \]. Dividing both sides by -1 gives \[ x^3 = 2 - y \]. Finally, solve for \( x \) by taking the cube root of both sides: \[ x = \sqrt[3]{2 - y} \].
03
Swap x and y
To express \( x \) in terms of \( y \), we now swap the roles of \( x \) and \( y \). This gives us the inverse function: \[ y = \sqrt[3]{2 - x} \]. So, the inverse function can be written as \( f^{-1}(x) = \sqrt[3]{2 - x} \).
04
Write the Inverse Function
Finally, write the expression for the inverse function we found in the previous step: \[ f^{-1}(x) = \sqrt[3]{2 - x} \] This is the inverse of the original function.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Cubic Functions
Cubic functions are a type of polynomial function where the highest degree of the variable is three. These functions have the general form \[ f(x) = ax^3 + bx^2 + cx + d \]where \(a\), \(b\), \(c\), and \(d\) are constants, and \(a eq 0\). The specific function we are dealing with, \( f(x) = -x^3 + 2 \), is a simplified cubic function where the coefficients \(b\) and \(c\) are zero.
- Cubic functions can have up to three real roots, or solutions, due to their high degree.
- Their graphs possess a characteristic 'S' shape and can cross the x-axis up to three times.
- These functions often model situations in physics and engineering due to their complex yet smooth transitions.
Function Notation
Function notation is a compact and elegant way to depict relationships between variables. Instead of expressing functions in a lengthy sentence, we use function notation to simplify this process.
- The notation \(f(x)\) represents a function named \(f\) where \(x\) is the input variable.
- The output, or the result of substituting \(x\) in the function, is usually dependent on a formula or rule defined for \(f\).
- In our case, \(f(x) = -x^3 + 2\) shows that to find the function's output, you substitute \(x\) into \(-x^3 + 2\).
Solving Equations
Solving equations is a fundamental skill in algebra that involves finding the value of variables that satisfy a given equation. For our exercise, solving equations involved manipulating the equation to find the inverse function.
- First, replace \(f(x)\) with \(y\), creating the equation \(y = -x^3 + 2\).
- The goal is to solve for \(x\) in terms of \(y\). This means rewriting the equation so that \(x\) is isolated on one side.
- We do this by isolating terms, changing signs, and taking cube roots: \(x^3 = 2 - y\), which simplifies to \(x = \sqrt[3]{2 - y}\).
Algebraic Manipulation
Algebraic manipulation refers to the process of rearranging and simplifying equations to solve for a variable or to express the relationship between variables differently. This skill becomes particularly useful when finding inverse functions.
- In our example, we needed to manipulate \(y = -x^3 + 2\) to solve for \(x\). This involved moving terms across an equal sign and changing operations, such as moving from addition to subtraction.
- Taking the cube root is a form of algebraic manipulation used to "undo" the cube in \(x^3\).
- Mastering algebraic manipulation allows you to swap variables, as we did by exchanging \(x\) and \(y\), resulting in a new inverse function representation.