Question

Which of the following relations is a function?
a. { (1, 2), (1, 3), (1, 4), (1, 5) }
b. { (1, 3), (2, 3), (4, 3), (9, 3) }
c. { (5, 4), (-6, 5), (4, 5), (4, 0) }
d. { (6, -1), (1, 4), (2, 3), (6, 1) }

Answer 1

the first one is not because its a one-to-many relation
(you 1 --> , 1--->3 and 2 others

Answer 2

a function is either one-to-one or many-to-one