Not writing the inverse function correctly

Oct 13, 2025 by wbrum.org 8 views

What is the Inverse of the Function $f(x) = \frac{1}{3}x - 5$ ?

Understanding the Concept of Inverse Functions

In mathematics, an inverse function is a function that reverses the operation of another function. In other words, if we have a function $f(x)$ , its inverse function $f^{-1}(x)$ will take the output of $f(x)$ and return the original input. Inverse functions are denoted by a superscript $-1$ and are used to solve equations and find the values of unknown variables.

The Given Function

The given function is $f(x) = \frac{1}{3}x - 5$ . To find the inverse of this function, we need to follow a series of steps that will help us reverse the operation of the function.

Step 1: Replace $f(x)$ with $y$

The first step in finding the inverse of a function is to replace the function with a variable, usually $y$ . So, we replace $f(x)$ with $y$ and get $y = \frac{1}{3}x - 5$ .

Step 2: Swap $x$ and $y$

The next step is to swap the variables $x$ and $y$ . This means that we replace $x$ with $y$ and $y$ with $x$ . So, we get $x = \frac{1}{3}y - 5$ .

Step 3: Solve for $y$

Now, we need to solve for $y$ . To do this, we first add $5$ to both sides of the equation, which gives us $x + 5 = \frac{1}{3}y$ . Then, we multiply both sides by $3$ to get rid of the fraction, which gives us $3(x + 5) = y$ . Expanding the left side, we get $3x + 15 = y$ .

Step 4: Write the Inverse Function

Now that we have solved for $y$ , we can write the inverse function. The inverse function is denoted by $f^{-1}(x)$ and is equal to $3x + 15$ .

Conclusion

In conclusion, the inverse of the function $f(x) = \frac{1}{3}x - 5$ is $f^{-1}(x) = 3x + 15$ . This means that if we plug in a value of $x$ into the inverse function, we will get the original value of $x$ that was plugged into the original function.

Answer

The correct answer is D. $f^{-1}(x) = 3x + 15$ .

Why is the Inverse Function Important?

The inverse function is important because it allows us to solve equations and find the values of unknown variables. For example, if we have an equation $f(x) = 2$ , we can plug in the value of $x$ into the inverse function to find the original value of $x$ that was plugged into the original function.

Real-World Applications of Inverse Functions

Inverse functions have many real-world applications, such as:

Physics: Inverse functions are used to describe the motion of objects under the influence of forces.
Engineering: Inverse functions are used to design and optimize systems, such as electrical circuits and mechanical systems.
Computer Science: Inverse functions are used in algorithms and data structures to solve problems and find solutions.

Common Mistakes to Avoid

When finding the inverse of a function, there are several common mistakes to avoid:

Not swapping $x$ and $y$ : This is the most common mistake when finding the inverse of a function. Make sure to swap $x$ and $y$ in the second step.
Not solving for $y$ : Make sure to solve for $y$ in the third step.
Not writing the inverse function correctly: Make sure to write the inverse function correctly in the fourth step.

Conclusion

In conclusion, finding the inverse of a function is an important concept in mathematics that has many real-world applications. By following the steps outlined in this article, you can find the inverse of a function and solve equations and find the values of unknown variables.
Q&A: Inverse Functions

Frequently Asked Questions

In this article, we will answer some of the most frequently asked questions about inverse functions.

Q: What is an inverse function?

A: An inverse function is a function that reverses the operation of another function. In other words, if we have a function $f(x)$ , its inverse function $f^{-1}(x)$ will take the output of $f(x)$ and return the original input.

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

A: To find the inverse of a function, you need to follow these steps:

Replace the function with a variable, usually $y$ .
Swap $x$ and $y$ .
Solve for $y$ .
Write the inverse function.

Q: What is the difference between a function and its inverse?

A: A function and its inverse are two different functions that are related to each other. The function takes an input and produces an output, while its inverse takes the output and produces the original input.

Q: Why is the inverse function important?

A: The inverse function is important because it allows us to solve equations and find the values of unknown variables. For example, if we have an equation $f(x) = 2$ , we can plug in the value of $x$ into the inverse function to find the original value of $x$ that was plugged into the original function.

Q: Can I find the inverse of any function?

A: No, not all functions have an inverse. For example, the function $f(x) = x^2$ does not have an inverse because it is not one-to-one.

Q: How do I know if a function has an inverse?

A: A function has an inverse if it is one-to-one, meaning that each output corresponds to exactly one input. You can check if a function is one-to-one by graphing it and checking if it passes the horizontal line test.

Q: What is the horizontal line test?

A: The horizontal line test is a test used to determine if a function is one-to-one. If a horizontal line intersects the graph of the function at more than one point, then the function is not one-to-one and does not have an inverse.

Q: Can I find the inverse of a function that is not one-to-one?

A: No, you cannot find the inverse of a function that is not one-to-one. The inverse function is only defined for one-to-one functions.

Q: How do I find the inverse of a function that is a composition of two functions?

A: To find the inverse of a function that is a composition of two functions, you need to find the inverse of each function separately and then compose them.

Q: Can I find the inverse of a function that is a rational function?

A: Yes, you can find the inverse of a rational function. To do this, you need to follow the same steps as finding the inverse of a linear function.

Q: What is the difference between the inverse of a function and the reciprocal of a function?

A: The inverse of a function and the reciprocal of a function are two different things. The inverse of a function is a function that reverses the operation of another function, while the reciprocal of a function is the function with the input and output swapped.

Q: Can I find the inverse of a function that is a trigonometric function?

A: Yes, you can find the inverse of a trigonometric function. To do this, you need to follow the same steps as finding the inverse of a linear function.

Conclusion

In conclusion, inverse functions are an important concept in mathematics that have many real-world applications. By following the steps outlined in this article, you can find the inverse of a function and solve equations and find the values of unknown variables.