SOLUTION: how do u now which is a function or not 0 0 1 1 -1 2 2 -2

Function is a relation in which each element of the domain is paired with 

EXACTLY one element of the range.



        example



           x      y

           0     -1

           2     -2 

           1     -1

           1      5 

          -3      4



This is not a function because the domain 1 is paired with two ranges -1 and 5.



A function should be



          x      y

          1      7

          2      7

          3      8



even if two domain has one element of y. 

domain is paired with exactly one range.