Question

Which of the following relations is a function?

A { (2, 6), (3, 9), (4, 2), (3, 6) }
B { (2, 8), (3, 6), (2, 4), (0, 2) }
C { (3, -2), (4, 7), (-2, 5), (-4, 5) }
D { (4, 7), (-2, 5), (1, 3), (-2, 1)

Please tell me how to tell (:

Answer 1

the first number in a pair is an element of the domain and the second is one in the range
if an element in the domain maps on to more than one element in the range this is a one-many relation and is not a function
so check the first relation - it is one-to-many Can you see why?

Answer 2

Yes, because of the '6' value, correct?

Answer 3

How do I single out one as a function though?

Answer 4

ok a function will either be one-to-one or many-to-one.

Answer 5

no the first one is a one-to-many because 3 maps to 6 and also 3 maps to 9

Answer 6

(3,6) and (3,9)

Answer 7

note that D is also one-to-many because of the (-2,5) and (-2,1)