Which set of ordered pairs represents a function?
{(-2,5), (6,9), (8, –4), (8, 7)}
{(-1,4), (-5, -2), (6,1),(-2,-2)}
{(-5, -6), (-5,3), (-7, -8), (-1, -9)}
{(-8, -4), (-8, –5), (-6, -1),(3,6)}
Please help
