Observe the mapping:

The set of ordered pairs are.

Domain:

The domain of the relation is the set of all first (-coordinates) coordinates.

The domain of the relation is .

Range:

The range of the relation is the set of second (-coordinates) coordinates.

The range of the relation is  .

Function:

Yes;

Each element of the domain is paired with one element of the range.

One -to-one function.

No;

Each element of the domain is not paired with exactly one unique element of the range.

The value and in the domain is paired with in the range.

Onto:

Yes;

Because each element of the range corresponds to an element of the domain.

The relation is a function.

No, relation is a not an one-to-one function.

Yes, relation is an onto function.