A function f maps ( 3,5,7,9) onto ( 0,2,4 ). Could f be represented by (3,0),(5,2). (7,4), (9,2)?
Yes, it is an onto mapping because 5 and 9 can be mapped to 2.
In mathematics, a function f from a set X to a set Y is surjective, if for every element y in the codomain Y of f, there is at least one element x in the domain X of f such that f(x) = y. It is not required that x be unique; the function f may map one or more elements of X to the same element of Y.