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4: DIFFERENTIATING BETWEEN RELATIONS and FUNCTIONS: SETS OF POINTS


IMPORTANT RULE: The difference between a function and a relation is that in a function, each x has one single corresponding y while in a relation, an x can have more then one corresponding y.


3. Function:(1, 4), (3,2), (-2, 7), (0, 9).
There are no 2 points having the same x coordinate.

     

4. Not a Function:(2, 5), (3,2), (-4, 9), (0, -5), (3, 6).
Same x coordinate appears twice. For x = 3, y = both 2 and 6.
This is a relation.

CONCEPT CHECK: Observe carefully representation number 3. To what number will you replace the input "1" from the first pair, to change the function into a relation? Write an appropriate number.