so if you're looking at points trying to determine if they're a function for example: (9,8), (10,2)
you have to make sure that the x is never the same in any of the points. like the first number (9 and 10) cant be the same or else it isnt a function.
if you're looking at it on a graph, you can use the pencil check, you run your pencil or a ruler(something straight) across the graph, and if it touches more than one point at once, then it isn't a function
if you're looking at it from a chart with two bubbles and lines, the lines can't come out of the same number more than once on the left bubble
