We have the following:
A relation is the correspondence of a first set, called Domain, with a second set, called Path or Range, so that each element of the Domain corresponds to one or more elements of the Path or Range.
For its part, a Function is a relation to which the condition is added that each value of the Domain corresponds to one and only one value of the Route.
From the previous definitions we can deduce that all functions are relations, but not all relations are functions.
We must also add that every equation is a Relationship, but not every equation is a Function.
In this case, each value of x (domain) corresponds to each value of y (range), therefore if it is a function