Check if the function is injective

Oct 13, 2025 by wbrum.org 126 views

The One-to-One Functions g(x) and h(x): Understanding the Definitions and Properties

In mathematics, functions play a crucial role in modeling real-world phenomena and solving problems. One-to-one functions, in particular, are an essential concept in mathematics, and understanding their properties is vital for solving various mathematical problems. In this article, we will explore the one-to-one functions g(x) and h(x) and discuss their definitions, properties, and how to determine if a function is one-to-one.

Definition of One-to-One Functions

A one-to-one function, also known as an injective function, is a function that maps each element of its domain to a unique element in its range. In other words, a function is one-to-one if it assigns distinct outputs to distinct inputs. This means that if f(x) = f(y), then x = y. In mathematical notation, a function f is one-to-one if:

f(x) = f(y) → x = y

The Function g(x)

The function g(x) is defined as:

g(x) = (x + 13)/5

To determine if g(x) is one-to-one, we need to check if it assigns distinct outputs to distinct inputs. Let's consider two arbitrary inputs x and y. If g(x) = g(y), then we can write:

(x + 13)/5 = (y + 13)/5

Multiplying both sides by 5, we get:

x + 13 = y + 13

Subtracting 13 from both sides, we get:

x = y

This shows that if g(x) = g(y), then x = y, which means that g(x) is one-to-one.

The Function h(x)

The function h(x) is defined as:

h = {(-6, 5), (-3, -9), (5, -5), (9, 0)}

To determine if h(x) is one-to-one, we need to check if it assigns distinct outputs to distinct inputs. Let's consider the inputs -6, -3, 5, and 9. We can see that h(-6) = 5, h(-3) = -9, h(5) = -5, and h(9) = 0. Since each input corresponds to a unique output, we can conclude that h(x) is one-to-one.

Properties of One-to-One Functions

One-to-one functions have several important properties, including:

Injectivity: A one-to-one function is injective, meaning that it assigns distinct outputs to distinct inputs.
Surjectivity: A one-to-one function is not necessarily surjective, meaning that it may not assign every possible output to some input.
Bijectivity: A one-to-one function is bijective if it is both injective and surjective.

How to Determine if a Function is One-to-One

To determine if a function is one-to-one, we can use the following steps:

Check if the function is injective: If the function assigns distinct outputs to distinct inputs, then it is injective.
Check if the function is surjective: If the function assigns every possible output to some input, then it is surjective.
Check if the function is bijective: If the function is both injective and surjective, then it is bijective.

Examples of One-to-One Functions

Some examples of one-to-one functions include:

Linear functions: Linear functions of the form f(x) = ax + b, where a ≠ 0, are one-to-one.
Polynomial functions: Polynomial functions of the form f(x) = a_n x^n + a_(n-1) x^(n-1) + ... + a_1 x + a_0, where a_n ≠ 0, are one-to-one.
Rational functions: Rational functions of the form f(x) = p(x)/q(x), where p(x) and q(x) are polynomials and q(x) ≠ 0, are one-to-one.

In our previous article, we discussed the concept of one-to-one functions and their properties. In this article, we will provide a Q&A guide to help you understand one-to-one functions better. We will answer some common questions related to one-to-one functions, including their definition, properties, and examples.

Q: What is a one-to-one function?

A: A one-to-one function, also known as an injective function, is a function that maps each element of its domain to a unique element in its range. In other words, a function is one-to-one if it assigns distinct outputs to distinct inputs.

Q: How do I determine if a function is one-to-one?

A: To determine if a function is one-to-one, you can use the following steps:

Check if the function is injective: If the function assigns distinct outputs to distinct inputs, then it is injective.
Check if the function is surjective: If the function assigns every possible output to some input, then it is surjective.
Check if the function is bijective: If the function is both injective and surjective, then it is bijective.

Q: What are some examples of one-to-one functions?

A: Some examples of one-to-one functions include:

Linear functions: Linear functions of the form f(x) = ax + b, where a ≠ 0, are one-to-one.
Polynomial functions: Polynomial functions of the form f(x) = a_n x^n + a_(n-1) x^(n-1) + ... + a_1 x + a_0, where a_n ≠ 0, are one-to-one.
Rational functions: Rational functions of the form f(x) = p(x)/q(x), where p(x) and q(x) are polynomials and q(x) ≠ 0, are one-to-one.

Q: Can a function be both one-to-one and onto?

A: Yes, a function can be both one-to-one and onto. In fact, a function that is both one-to-one and onto is called a bijective function.

Q: How do I find the inverse of a one-to-one function?

A: To find the inverse of a one-to-one function, you can use the following steps:

Swap the x and y variables: Swap the x and y variables in the function.
Solve for y: Solve for y in the resulting equation.
Write the inverse function: Write the inverse function in terms of x.

Q: What are some common mistakes to avoid when working with one-to-one functions?

A: Some common mistakes to avoid when working with one-to-one functions include:

Confusing injectivity and surjectivity: Make sure to distinguish between injectivity and surjectivity when working with one-to-one functions.
Not checking for bijectivity: Make sure to check if a function is bijective before using it in a mathematical proof.
Not using the correct notation: Make sure to use the correct notation when working with one-to-one functions.

In conclusion, one-to-one functions are an essential concept in mathematics, and understanding their properties is vital for solving various mathematical problems. We hope that this Q&A guide has helped you understand one-to-one functions better and has provided you with a solid foundation for working with these functions.