Question

. Which of the following relations is NOT a function?


A. (-7,4), (3, 3), (-2, 1), (9, 2)


B. (9,4), (-2, 2), (3, 1), (-7, 2)


C. (3,4), (-2, 2), (3, 1), (-7, 2)


D. (-2,4), (3, 2), (9, 1), (-7, 5)

Answer 1

Something is a function if you can always answer the question "For a given X, what's the value of Y"?

(1, 2) (3, 2) --> What's the value if x=1? It's 2. What's the value if x=3? It's 2. Since you can always answer the question, it's a function.

(1, 8) (1, 9) --> What's the value if x=1? You don't know. it could be either 8 or 9. Therefore it's not a function.