Question

Which relation is a function?

{(1, 4), (2, 3), (3, 2), (4, 1)}

{(4, 2), (3, 3), (2, 4), (3, 2)}

{(1, −1), (−2, 2), (−1, 2), (1, −2)}

{(1, 2), (2, 3), (3, 2), (2, 1)}

Answer 1

The first one

Explanation:

A function can't have the x coordinate (first number in parentheses) repeated with a different y value. All of the others have that.