By using graphs. Because the domain refers to the set of possible input values, the domain of a graph consists of all the input values shown on the x-axis. The range is the set of possible output values, which are shown on the y-axis.
The domain is {-8}
The range is {5,6,7,8}
The relation is not a function as the domain value -8 maps to multiple values. All domain values in a relation needs to map to exactly one range value for it be a function.
