Question

what do you mean by function is injectivity or subjectivity ?

Answer 1

1.The function is injective (one-to-one) if each element of the codomain is mapped to by at most one element of the domain. An injective function is an injection. Notationally:{\displaystyle \forall x,x'\in X,f(x)=f(x')\Rightarrow x=x'.}Or, equivalently (using logical transposition),{\displaystyle \forall x,x'\in X,x\neq x'\Rightarrow f(x)\neq f(x').

2.The function is surjective (onto) if each element of the codomain is mapped to by at least one element of the domain. (That is, the image and the codomain of the function are equal.) A surjective function is a surjection. Notationally:{\displaystyle \forall y\in Y,\exists x\in X{\text{ such that }}y=f(x).}

Answer 2

I hope it may help you