A graph represents a function when each input value corresponds to a unique output value. To determine if a graph represents a function, use the vertical line test.
A graph represents a function when each input value (x) corresponds to a unique output value (y). To determine if a graph represents a function, we can use the vertical line test.
If a vertical line passes through the graph at more than one point, then it is not a function. However, if every vertical line passes through the graph at most once, then it is a function.
For example, the graph should pass the vertical line test:
Graph of a function:
(Sample graph of a straight line going up and to the right)
Graph that is not a function:
(Sample graph of a circle)