which of the following sets of ordered pairs define a function? a. {(3,2),(-3,6),(3,-2),(-3,-6)}
b. {(1,2),(2,6),(3,-2),(4,-6)}
c. {(2,2),(2,3),(2,4),(2,-9)}
d. {(4,4),(-3,4),(4,-4),(-3,-4)}​