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). |
4. Not a Function:(2, 5), (3,2), (-4, 9), (0, -5), (3, 6). |

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.