Chapter 10: Problem 1
Complete each statement, or answer the question. For a function to have an inverse, it must be ____.
Short Answer
Expert verified
One-to-one (bijective).
Step by step solution
01
Understand the Concept of Function Inverses
To determine if a function has an inverse, remember that an inverse function reverses the operation of the original function. For a function to have an inverse, every output must be attributable to exactly one input.
02
Define the One-to-One Property
A function is one-to-one (bijective) if each element of its domain is mapped to a unique element in its codomain. This means there are no repeated y-values for different x-values.
03
Apply the Horizontal Line Test
A practical way to check if a function is one-to-one is to use the horizontal line test. If every horizontal line crosses the graph of the function at most once, then the function is one-to-one and, therefore, has an inverse.
04
Conclusion
Conclude that for a function to have an inverse, it must be a one-to-one function, meaning it passes the horizontal line test and satisfies the one-to-one property.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
One-to-One Function
A one-to-one function, also known as an injective function, is a function where each element of the domain maps to a unique element in the codomain. This means that no two different inputs can produce the same output.
For example, consider a function \( f(x) = 2x + 3 \). If \( f(x_1) = f(x_2) \), then \( 2x_1 + 3 = 2x_2 + 3 \). Solving this gives \( x_1 = x_2 \), showing that \( f(x) \) is one-to-one because different inputs do not yield the same output.
Recognizing a one-to-one function involves checking that:
For example, consider a function \( f(x) = 2x + 3 \). If \( f(x_1) = f(x_2) \), then \( 2x_1 + 3 = 2x_2 + 3 \). Solving this gives \( x_1 = x_2 \), showing that \( f(x) \) is one-to-one because different inputs do not yield the same output.
Recognizing a one-to-one function involves checking that:
- Each output has one and only one corresponding input.
- No two distinct inputs share the same output.
Horizontal Line Test
The horizontal line test is a visual method used to determine whether a function is one-to-one. If every horizontal line crosses the graph of the function at most once, then the function is one-to-one and can have an inverse.
This is because a horizontal line that crosses the graph more than once means there are multiple inputs yielding the same output, which contradicts the one-to-one property.
Here's how to apply the horizontal line test:
This is because a horizontal line that crosses the graph more than once means there are multiple inputs yielding the same output, which contradicts the one-to-one property.
Here's how to apply the horizontal line test:
- Draw a series of horizontal lines across the function's graph.
- Observe each line to ensure it intersects the graph no more than once.
Bijective Function
A bijective function is both one-to-one and onto, making it a powerful type of function in mathematics. Bijective functions have a unique feature: they have inverses.
To be bijective, a function must satisfy two conditions:
To be bijective, a function must satisfy two conditions:
- One-to-One (Injective): Each output is produced from a unique input, as discussed earlier.
- Onto (Surjective): Every element in the codomain is mapped by an element in the domain.
- The inverse will map each element of the codomain back to a unique element of the domain.
- Every element in the codomain has a preimage in the domain.