Hello!
A function is a relation where each x value (domain) can only be associated with one y value (range). It is okay for a y value to have multiple x values.
Looking at your relations, we can use this to determine what is a function.
Relation 1: each x value seems to be only associated with one range, so I'd say relation one is a function.
Relation 2: The domain of 3 is associated with both pen and lake, therefore, relation two is not a function.
Relation 3: There is only one point for each of the domains, so relation 3 is a function.
Relation 4: There also seems to only be one point for each one of the domains, so relation 4 is a function.
Hope this helps!
