Question

Which set of ordered pairs represents a function?

{(2, –2), (1, 5), (–2, 2), (1, –3), (8, –1)}
{(3, –1), (7, 1), (–6, –1), (9, 1), (2, –1)}
{(6, 8), (5, 2), (–2, –5), (1, –3), (–2, 9)}
{(–3, 1), (6, 3), (–3, 2), (–3, –3), (1, –1)}

Answer 1

The second set: {(3, –1), (7, 1), (–6, –1), (9, 1), (2, –1)}.

Reason: each input (first coordinate) appears only once. The other sets repeat x-values (e.g. x=1 in the first set, x=–2 in the third, x=–3 in the fourth), so they are not functions.