Скачать или смотреть Vertical and Horizontal Line Test

You’ve probably been using the vertical line test to tell if a graph represents a function. The horizontal line test is the same thing just with a horizontal line. If the graph passes the vertical and horizontal line tests, it is a one-to-one function. Why do we care? Well, a one-to-one function has an inverse and these are probably coming in your future
Explanation:

You’ve probably been using the vertical line test to tell if a graph represents a function. The horizontal line test is the same thing, but with a horizontal line.

If the graph passes the vertical line test, it means that for each x-value, there is only one corresponding y-value, which makes it a function.
If the graph also passes the horizontal line test, it means that for each y-value, there is only one corresponding x-value, making the function one-to-one.

Why do we care?

A one-to-one function has an inverse function. This is important because inverse functions "reverse" the operation of the original function, which is useful in solving equations and in many applications across mathematics and science.