To determine the domain of a function from the graph, identify the set of all the x-coordinates in the function’s graph.

a graph of a line segment with endpoints at (0, 8) and (4, 0) is shown

In this example, the domain is {0 < x < 4} since 0 is the least x-value and 4 is the greatest x-value.

To determine the range of a function from the graph, identify the set of all the y-coordinates in the function’s graph.

In this example, the range is {0 < y < 8} since 0 is the least y-value and 8 is the greatest y-value.

Additional Example

In this example, the domain is {0,1,2,3} and the range is {0,3,6,9}.

a graph with points at (0, 0), (1, 3), (2, 6), and (3, 9) is shown