Which relation is not a function?
A. {(2, 4), (1, 2), (0,0), (-1,2), (-2,4)}
B. {(2,4), (1, 1), (0,0), (-1, 1), (-2,4)}
C. {(2, 2), (1, 1), (0,0), (-1,1), (-2, 2)}
D. {(2, 2), (1, 1), (0,0), (1,-1), (2,-2)}
We have the two points (2,2) and (2,-2) which have a repeated x coordinate. This is not allowed if we wanted a function. A function must have any x input lead to exactly one and only one output (assuming the input is in the domain).
