How can you tell if a relation is a function

One way to tell if a relation is a function is by using something called the vertical line test. In other words, if we can draw a vertical that passes through more than one point on a graph, then the relation does not represent a function. Another way to tell if a relation represents a function is by looking at the X coordinates of each ordered pair. If any of the ordered pairs have the same X coordinate, then the relation is not a function.

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