contestada

Which of the following sets of ordered pairs represents a function?

{(-6,-1), (13,8), (1,6), (1,-10)}

{(10,5), (10,-5), (5,10), (5,-10)}

{(3,5), (-17,-5), (3,-5), (-17,5)}

{(10,5), (-10,-5), (5,10), (-5,-10)}