Hi there! The way to determine if a set of ordered pairs represents a function is just to pay attention to the x-coordinate, the first value in the ordered pair. A function is defined as when every x has exactly one y. Let's examine the sets:
1) {(2, –2), (1, 5), (–2, 2), (1, –3), (8, –1)} -- you see here that there are the points (1,5) & (1, -3), so no function
2) {(3, –1), (7, 1), (–6, –1), (9, 1), (2, –1)} -- each x is unique, so this is a function
3) {(6, 8), (5, 2), (–2, –5), (1, –3), (–2, 9)} -- you see here that there are the points (-2, -5) & (-2, 9), so no function
4) {(–3, 1), (6, 3), (–3, 2), (–3, –3), (1, –1)} -- you see here that there are the points (-3, 1), (-3,2), & (-3,3) - with 3 of the same x coordinate, is NOT a function.
There you have it! Only set 2 is a function.
