Vertical line test

Imagine you are playing a game of connect the dots with a bunch of dots on a piece of paper. You have to draw lines between the dots to make a picture. Now imagine there are some dots that are very close together, so close that you could draw a straight line between them without touching any other dots.

If you can draw a straight line from any point on the picture to another point on the picture without touching any other points, then it passes the vertical line test.

For example, if you drew a line from the top of a circle to the bottom of a circle and it touched the circle somewhere else, then it would not pass the vertical line test. But if you drew a line from the top of a square to the bottom of a square and it didn't touch any other parts of the square, then it would pass the vertical line test.

The vertical line test helps us figure out if a shape is a function or not. A function is like a rule that tells us what to do with each number we put in. For example, if we have a function that multiplies any number we put in by 2, then we can know what the answer will always be when we put in different numbers.

When we use the vertical line test on a function, we are checking to see if there is more than one answer for a given input. If there is, then it means the shape is not a function because it doesn't follow the rules of having only one output for each input.

So basically, the vertical line test helps us see if shapes pass or fail the rules of being a function.