Question

Which of the sets of ordered pairs represents a function?

A = {(–4, 5), (1, –1), (2, –2), (2, 3)}

B = {(2, 2), (3, –2), (9, 3), (9, –3)}

Answer 1

A function should work as such.

(X, Y), (X, Y), (X, Y), (X, Y)

Each X should have only one Y.

Therefore if we fill in these letters with numbers.

(3, 1), (2, 4), (5, 8), (4, 9)

We can safely say that this is a function as each X has only one Y.

However, if it looked like this,

(3, 1), (2, 4), (5, 8), (3, 9)

It would not be a function as X=3 has two Y's. Y = 1 and Y = 9.

Answer 2

If you see two or more ordered pairs using the same x-coordinate, it is NOT a function.
To be a function, you can only use a specific value of an x-coordinate once.