Chapter 4: Problem 22
If \(\mathrm{g}=\\{(x, y) : y=7-x\\},\) find \(\mathrm{g}^{-1}\) if it exists. Is it possible for a function to be its own inverse?
Short Answer
Expert verified
The inverse is the same function, \( g^{-1}(x) = 7 - x \). Yes, a function can be its own inverse.
Step by step solution
01
Understanding the Inverse Function
To find the inverse of a function, we need to swap the roles of the domain and the range. This means that instead of having an equation where y is expressed in terms of x, we need a new function where x is expressed in terms of y. For the function \( y = 7 - x \), we need to solve for x in terms of y.
02
Solving for x in Terms of y
Start by expressing x in terms of y from the equation \( y = 7 - x \). Rearrange this equation to solve for x. Add x to both sides to get \( y + x = 7 \), then subtract y from both sides to obtain \( x = 7 - y \).
03
Finding the Inverse Function
Now that we have expressed x in terms of y (\( x = 7 - y \)), swap x and y to find the inverse function. Replace x with y and y with x, resulting in the inverse function \( y = 7 - x \).
04
Check If the Function is Its Own Inverse
Notice that the original function \( y = 7 - x \) and the inverse function \( y = 7 - x \) are identical. This confirms that the function is indeed its own inverse.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Function Inversion
Function inversion is a process where we reverse the roles of the input and output in a function. When we talk about a function, we typically have a relationship between two sets of numbers or variables, where every input from the first set is assigned to exactly one output in the second set. Inverting a function involves swapping these assignments, making the output act as the new input and vice versa.
- Start with a function in the form of an equation, like the function given in the exercise, \( y = 7 - x \).
- The goal is to express the original input variable \( x \) in terms of the output variable \( y \).
- By rearranging the original equation, you solve for \( x \) as \( x = 7 - y \).
- Finally, you swap the variables again to write the inverse function, resulting in \( y = 7 - x \).
Domain and Range
In any function, domain and range play vital roles. The domain is the set of all possible input values (\( x \)-values) for which the function is defined. Conversely, the range is the set of all possible output values (\( y \)-values) the function can produce. When we find the inverse of a function, these sets swap their roles.In our function \( y = 7 - x \):
- The domain is all real numbers, since \( x \) can be any value.
- The range is also all real numbers because \( y \) takes on every value as \( x \) varies.
Self-Inverse Functions
A function is termed 'self-inverse' if it acts as its own inverse. This means applying the function twice returns you to your original input value. In mathematical terms, if the function \( f(x) \) satisfies \( f(f(x)) = x \) for all inputs \( x \) in its domain, it is self-inverse.In the exercise, the function \( y = 7 - x \) turns out to be its own inverse because its inverse is identical to the original function.
- Such functions are neat and elegant in mathematics.
- Common examples of self-inverse functions are \( f(x) = -x \) and \( f(x) = \frac{1}{x} \) where these functions map an input to itself after two applications.