Which set of ordered pairs does not represent a function?
{(5, -9), (6, -6),(-3, 8), (9,-6)}
{(-6, -4), (4, -8),(-6,9), (1, -3)}
{(1, -1), (-5,7), (4,-9), (-9,7)}
{(8,-9), (-3, -6), (-4, 4), (1, -5)}