Decide wether or not if these are functions

Relation 1: Not a Function

Relation 2: Not a Function

Relation 3: Function

Relation 4: Not a Function

Explanation:

There can only be one output (what you get out of it) for each input (what you put into the function) in a function.

step-by-step explanation:

step 1: solve one of the equations for one of the variables. let's solve the first equation for y:

step 2: substitute that equation into the other equation, and solve for x.

step 3: substitute x = 4 x = 4 x=4 into one of the original equations, and solve for y.