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# Let N be the set of natural numbers and the relation R be defined on N such that R = {(x, y) : y = 2x, x, y $\in$ N}.  What is the domain, co-domain and range of R? Is this relation a function?

The domain of R is the set of natural numbers N.
The co-domain is also N. The range is the set of even natural numbers.
Since every natural number n has one and only one image, this relation is a function.