Question

is the relation a function? if so please explain.

{(3,1), (5,3), (7,7), (3,5)}

Answer 1

no

Answer 2

Because you have two different y values for the x value 3
ie (3,1) and (3,5)

Answer 3

You need to check if there is one output for every input. x is the input, y is the output (x,y).