Question

Which of the following sets represent a function?
{(3,5), (-1,7), (3,9)}
{(1,2), (3,2), (5,7)}
{(1,2), (1,4), (1,6)}

Answer 1

do you know how to tell? is is very easy

Answer 2

inputs cannot have same output
or
outputs cannot have same inputs

(not both)

Answer 3

you tell by looking at the first numbers in each ordered pairs
if there is a repeated number, then NO
if all the first numbers are different, then YES