Question 1156721
mapping is writing the x and y in a column and drawing arrows from x to y based on the ordered pair.

When there are two values of y for the same x (a circle), it is not a function.
So all you have to do is see if the x-values are all different.  If they are, it is a function.  If not, they have to have the same y (same ordered pair) to be a function. 

Here, all the x values are different.  It is a function.