Question 74232
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Domain of a relation is the set of all its first element or x - coordintes.

Range of a relation is the set of all its second element or y-coordinates.

example 

          x       y
         -1       0
          0      1.5
          1       3

Domain: {-1, 0, 1}
Range: {0, 1.5, 3}


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 <u>exactly</u> one range