Question

Which relation is a function?

A. (3,4),(3,3),(1,2),(1,5)

B. (3,4),(2,4),(5,1),(3,5)

C. (1,3),(2,6),(3,9),(4,12)

D. (1,4),(1,3),(1,2),(1,1)

Answer 1

C

Explanation:

Look for the case in which every input is unique (no repetitions).

A does not qualify, as 3 appears as an input twice.

B does not qualify, for the same reason

C qualifies (is a function), because all the inputs {1, 2, 3, 4} are unique.

D does not qualify (see A, above).