How to Find the Inverse of a Function with a Fraction – Step-by-Step Simplification Guide

How to Find the Inverse of a Function with a Fraction Step-by-Step Simplification Guide

To find the inverse of a function with a fraction, I start by remembering that the inverse function undoes the action of the original function.

If my function is expressed as $y = \frac{a}{b}x + c $, where ( a ), ( b ), and ( c ) are constants, my goal is to solve for ( x ) in terms of ( y ).

This involves swapping the roles of ( x ) and ( y ), then solving the resulting equation for the new ( y ), which gives me the formula for the inverse of the function.

Next, I ensure that the function is one-to-one, which means that for every ( y ), there’s exactly one ( x ), and vice versa. This property is crucial because if a function isn’t one-to-one, it won’t have an inverse function that is also a function.

To check this, I can use the Horizontal Line Test or verify that the original function is either strictly increasing or decreasing.

A function being transformed into its inverse, with a fraction being flipped and reversed

There’s a unique satisfaction in charting the course back to the starting point, which is exactly what an inverse function allows me to do. Stay with me as I walk through the detailed steps to untangle and recast the original function into its inverse.

Steps to Find the Inverse of a Function with a Fraction

In this section, we’ll go through the necessary steps to find the inverse of a function with a fraction. The process involves changing the function‘s format, algebraically solving for the output variable, and doing a quick check to ensure we’ve correctly found the inverse.

Setting Up the Function for Inversion

To start with, let’s consider a function ( f(x) ) that is written as a fraction. I’ll first substitute ( f(x) ) with the variable ( y ). This helps me manipulate the function more easily.

Then, I’ll interchange the input and output variables. This means swapping ( x ) and ( y ) to set up the equation for solving for y.

Solving for Y and Identifying the Inverse

The next step is to solve the new equation for ( y ). This is where my algebra skills come into play. I need to isolate ( y ) on one side of the equation to find the inverse function.

This might include multiplying both sides of the equation to clear the denominator or performing other algebraic manipulations necessary for a rational function.

Once ( y ) is isolated, the newly arranged function is the inverse function of the original. I’ll then re-label ( y ) as $ f^{-1}(x) $ to denote it as the inverse.

Verifying the Inverse Function

Finally, it’s important to verify that the inverse function I have found is correct. To do this, I will use the horizontal line test on the graph of the original function to ensure it’s a one-to-one function, which is a necessary condition for a function to have an inverse.

Also, I can test the inverse by confirming that $f(f^{-1}(x)) = x $ and $ f^{-1}(f(x)) = x $. If both conditions are satisfied, the functions are indeed inverses of each other.

Remember, this is like a reflection over the line ( y=x ). If the original function and the inverse line up as mirror images over this line, it’s another visual confirmation that I’ve got it right.


Inverting a function can seem challenging, but I find it satisfying when the pieces fall into place. A crucial step in understanding a function’s behavior is to study its inverse, particularly when dealing with fractions.

Throughout our discussion, we’ve seen that by replacing ( y ) with ( f(x) ), and then interchanging ( x ) with ( y ), we can solve for the new ( y ), which represents $ f^{-1}(x) $.

Remember, the algebraic manipulation to isolate ( y ) involves standard operations: addition, subtraction, multiplication, division, and possibly factoring.

For functions with fractions, extra care must be taken to ensure that the process is done accurately, which may involve multiplying by the reciprocal or finding a common denominator.

The beauty of mathematics lies in such transformations of functions. From my experience, practicing with different functions sharpens the ability to find inverses quickly and correctly.

Should you wish to revisit the steps or require further examples, feel free to check out the related guide I’ve provided earlier in the article How to Effectively Find Functions Inverses.

Finally, be diligent in checking your work, as the correctness of an inverse is proven when $f(f^{-1}(x)) = x$ and $f^{-1}(f(x)) = x $. By plotting both the function and its inverse on a graph, one should see that they are reflections over the line ( y = x ).

With this, I hope that you feel more confident in tackling fractions within functions and their inverses. Keep practicing, and the processes will become second nature!