If , , and is the relation from to , where means , determine whether represents a function or not.
A function maps each element of a set (the domain) to exactly one element of another set (the range). In this problem, is the domain and is the range.
Substitute each element of for "" in the relationship .
Each element in maps on to exactly one element in , so does represent a function.
Note that it doesn't matter that there are extra elements in .