Bam K. answered • 07/29/16

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f : A →B is

**a function**if for any element of set A there exists one and only one element of set B . Knowledge of domain and range and the strict compliance of the definition would separate functions from mere mathematical expressions.A couple of examples: f: R→R with f(x)=x

^{2}^{ i}is a function; x^{2}+ y^{2}= 1 is not a function. It boils down to the strict definition of a function!