Question

Which relation describes a function? What makes it a function?
A)
{(2,3),(3,3),(3,4)} Each member of the domain and range is positive.
B)
{(-2,3),(-4,5),(-6,7)} Each member of the domain and range is unique.
C)
{(2,3),(3,3),(3,4)} Each member of the domain and range is a real number.
D)
{(-2,3),(-3,3),(-4,3)} Each member of the domain is assigned exactly one member of the range.

Answer 1

I think it could be A
or D

Answer 2

The definition of a function is that each member of the domain is assigned exactly one member of the range.
In other words, every x can only have one y. So in A, (3,3) and (3,4) don't make a function because when x=3, y=3 AND y=4 -- that can't happen in a function.