See this page ( http://www.algebra.com/algebra/homework/Functions/Functions.faq.question.393212.html ) for info on ordered pairs that do not model a function.
So ordered pairs are things like (1,2), (3,4), and so on.
Ordered pairs that model a function have to have the first coordinates (the 'x' in (x,y) ) all different. The second coordinates (the 'y' in (x,y) ) can have values that are the same.
For this problem we want four ordered pairs, so let's try:
(0,-5), (1,-6), (2,-7), (3,-8)
Those four ordered pairs do model a function because the first coordinates (0,1,2,3) are all different.
We want four ordered pairs that do *not* model a function, so there has to be at least one match between the first coordinates. We could do this:
(0,-5), (0,-6), (2,-7), (3,-8)
There are many possible solutions, but this one works because the first coordinates (0,0,2,3) have a repeat (two zeroes).