Find domain and range
For every relation, there are two important sets of elements called the domain and range.
Domain and Range
In a relation, the set of all values of the independent variable (x) is the domain. The set of all values of the dependent variable ( y) is the range.
Example
{(3, 21), (4, 2), (4, 5), (6, 8)}
The domain, the set of x-values, is {3, 4, 6}; the range, the set of y-values, is {21, 2, 5, 8}. This relation is not a function because the same x-value 4 is paired with two different y-values, 2 and 5.