For a function to have an inverse, the relationship must be that there is a 1-to-1 relationship between its input values and its output values. A quadratic equation doesn't have an inverse …

Learn what the inverse of a function is, and how to evaluate inverses of functions that are given in tables or graphs.

Sal explains what inverse functions are. Then he explains how to algebraically find the inverse of a function and looks at the graphical relationship between inverse functions.

Now the first thing you might ask is let's say that I have a function f, and there does exist a function f inverse that satisfies these two requirements. So f is invertible.

Intro to inverse functions Inputs & outputs of inverse functions Graphing the inverse of a linear function Finding inverse functions: linear

In the first inverse function video, I talked about how a function and their inverse-- they are the reflection over the line y equals x. So where's the line y equals x here?

Not all functions have inverses. Those who do are called "invertible." Learn how we can tell whether a function is invertible or not.

By starting out with a function, you know it passes the vertical line test by definition. However, for its inverse to be a function, it also has to pass the horizontal line test to insure the one-to-one …

Sal explains that if f (a)=b, then f ⁻¹ (b)=a, or in other words, the inverse function of f outputs a when its input is b.

Practice finding the formula of the inverse function of a given linear function.