Chapter 3: Problem 15
Assume that \(f\) is a one-to-one function. (a) If \(f(6)=17,\) what is \(f^{-1}(17) ?\) (b) If \(f^{-1}(3)=2,\) what is \(f(2) ?\)
Short Answer
Expert verified
(a) 6
(b) 3
Step by step solution
01
Understanding the Definition of Inverse Functions
A function \(f\) is called one-to-one if it passes the horizontal line test, meaning every \(y\) value has exactly one corresponding \(x\) value. The inverse of \(f\), denoted as \(f^{-1}\), essentially reverses this relationship.
02
Solving Part (a)
We know that \(f(6)=17\). The property of inverse functions tells us that if \(f(a)=b\), then \(f^{-1}(b)=a\). Therefore, since \(f(6)=17\), it follows that \(f^{-1}(17)=6\).
03
Solving Part (b)
The problem states \(f^{-1}(3)=2\). Using the definition of inverse functions, this means \(f(2)=3\), since if \(f^{-1}(b)=a\), then \(f(a)=b\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
One-to-One Function
To understand inverse functions, we start with the concept of a "one-to-one function." In simple terms, a one-to-one function ensures that every output (or second element in a pair) is paired uniquely with one input (or first element in a pair).
Imagine matching key to keyhole, where each key fits exactly one specific keyhole. In the context of functions:
Imagine matching key to keyhole, where each key fits exactly one specific keyhole. In the context of functions:
- Each value of the function's output corresponds to only one input.
- This uniqueness allows us to "reverse" the function with an inverse function.
Horizontal Line Test
To determine if a function is one-to-one, we can use a simple visual tool called the "Horizontal Line Test." This test allows us to see if a function qualifies for having an inverse.
The procedure is straightforward:
The procedure is straightforward:
- Imagine drawing 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 each horizontal line intersects the graph at most once, then the function is one-to-one.
Function Properties
Understanding function properties is key in working with inverses. Besides being one-to-one, knowing other properties can help to deal with inverse functions gracefully.
Here are some properties to consider:
Here are some properties to consider:
- Domain and Range: For a function and its inverse, the domain of the function becomes the range of the inverse and vice versa.
- Symmetry: Graphically, a function and its inverse are mirror images of each other across the line \( y = x \).
Inverse Relationship
An inverse relationship in mathematical functions is a fundamental concept where the operation can be "reversed." Inverse functions \( f \, \text{and} \, f^{-1} \) are pairs that satisfy this relationship.
Here's what to keep in mind:
Here's what to keep in mind:
- If \( f(a) = b \), then \( f^{-1}(b) = a \).
- This relationship allows us to determine unknowns. For example, if you know \( f(2) = 3 \), then \( f^{-1}(3) = 2 \).
- The notation \( f^{-1} \) does not mean \( 1/f \); it specifically represents the unique function that "undoes" \( f \).