Question

Determine if (1,2) (3,4) (5,5) is a function

Answer 1

It is a function because each input only has one output

Answer 2

To determine if something is a function or relation, you would look at the x values and determine if every x value has 1 y value. any x vaue with more than one y value would be a relation. 
this one would be a function because there only one y value for every x value