You really should learn what a function is. It will help you in most of your future math courses.
(input, output) = (domain, range)
An input CANNOT go to two different outputs. This is not a function.
If the output is repeated, no problem. It is still a function but not ONE-TO-ONE.
Relation 1 is not a function because -7 goes to three different outputs.
Relation 2 is not function because cloud goes to two different outputs. Cloud is mapped to -6 and 6. Not a function.
Relation 3 is a function but it is not ONE-TO-ONE. Do you know why based on what I said above?
Relation 4 is not a function because -9 goes to two different outputs.
Understand?
