Which of the following lists of ordered pairs is a function?

A. (0, 2), (4, 2), (0, -4), (4, -2)
B. (2, 4), (3, 9), (4, 16), (5, 25)
C. (2, 4), (-2, 4), (3, 9), (-2, -4)
D. (1, 1), (2, 3), (1, 5), (4, 7)

Question

Which of the following lists of ordered pairs is a function?

 		A.	(0, 2), (4, 2), (0, -4), (4, -2)
 		B.	(2, 4), (3, 9), (4, 16), (5, 25)
 		C.	(2, 4), (-2, 4), (3, 9), (-2, -4)
 		D.	(1, 1), (2, 3), (1, 5), (4, 7)

luffingsails · Answer

For these ordered pairs to be functions... every x value can only be mapped to one corresponding y value.

So, for instance in A, there is the ordered pair (0,2) and (0,-4). This can't be a function because x cannot map to two *different* values. Can you see others like this?