this week in math I learned how to identify functions.
You can identify them in different ways, depending on how your data is presented:
arrow diagram: if one input has more than one arrow it is not a function 
So in this example it is not a function because one input has more than one arrow pointing to an output.
Ordred pair: If you have more than one ordered pair with the same input value, but different outputs, its not an output. (2,3)(3,3)(4,3) is a function because all the input values are different.
Graphs: If it passes the vertical line test it is a function. If a vertical line passes the graph more than once it is not a function.
So in this example the image on the left doesn’t pass the vertical line test because a few vertical lines pass through the graph more than once. The image on the right does pass because the vertical lines only pass thought the graph once.
*One thing to always remember is that one output may correspond to multiple inputs and it will still be a function. *