Question

which set is a function?
A {(2,6), (3,6), (4,6), (2,0)}
B {(0,4), (0,9), (12,6), (-3,9)}
C {(6,2), (2,0), (4,6), (6,4)}
D {(0,2), (2,0), (4,6), (6,4)}
E {(0,3), (3,0), (0,4), (4,0)}

Answer 1

in order for a set to be a function, each x-value must be assigned to a unique y-value. for example, choice A would *not* be a function because (2,6) (2,0) assigns x = 2 to both y = 6 and y = 0 at once. see which answer choice does not have any x-values assigned to multiple y-values at a time.

shortcut method - see which answer choice has no repeats in x-values

Answer 2

D because none of the x values repeat. Whichever x value repeats that's how u tell it's not a function. So with no repeating x values is what a function is