Question

select all the relations that represent a function.
(1, 3), (2, 5), (2, 7) (4, 9)
(1, 3), (2, 5), (3, 7) (4, 9)
(1, 3), (1, 5), (1, 7) (4, 9)
(1, 3), (2, 3), (3, 3) (4, 3)
(1, 2), (2, 5), (2, 1) (4, 5)

Explanation:

Step1: Recall function definition

A relation is a function if every input (x-value) has exactly one output (y-value).

Step2: Check first relation

Input 2 maps to 5 and 7. Not a function.

Step3: Check second relation

Each x-value (1,2,3,4) has one y-value. Is a function.

Step4: Check third relation

Input 1 maps to 3,5,7. Not a function.

Step5: Check fourth relation

Each x-value maps to 3 (one output). Is a function.

Step6: Check fifth relation

Input 2 maps to 5 and 1. Not a function.

Answer:

(1, 3), (2, 5), (3, 7) (4, 9)
(1, 3), (2, 3), (3, 3) (4, 3)