Monday, 8 April 2013

analysis - Quick Clarification: Definition of Bijective Function

I am very familiar with the concepts of bijective, surjective and injective maps but I am interested in improvising the definition of bijection in a way I have not seen done before. To be clear I will provide the definitions that I use for surjective, injective and bijective although they are the common and generally accepted definitions.



f:AB is surjective yB, xA : f(x)=y.



f:AB is injective x,yA, f(x)=f(y)x=y



f:AB is bijective (yB, xA : f(x)=y) (x,yA, f(x)=f(y)x=y)




You can see that the definition provided for bijection is simply the conjunction of surjective and injection.




My question is, does it suffice to define bijection as such:



f:AB is bijective yB, !xA : f(x)=y.




Sorry for making a mountain out of a mole hill with this question, the person I usually work with is not here tonight so I have to run my spit ball ideas by you guys! Thanks in advance.

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