A relation is a function if and only if no same x-coordinate has two or more y-coordinates.
To help us determine whether the relation is a function, let's mapped out the coordinates using a table.
As we can see, no one x-coordinate has two or more y-coordinates.
In other words, what we can see in the table above, every unique x-coordinate is paired with a unique y-coordinate as well. Therefore, the given relation R is a function, specifically, a one-to-one function.