For a function to have an inverse function, it must be a one-to-one function, which means it must pass the horizontal line test. In other words, the function must strictly increase or strictly decrease over its entire domain.

So, how can you approach a function that isn't one-to-one? For instance, how could you determine an inverse function for the function f(x) = x²? If you were to somehow change the function, how would that affect the resulting inverse function?