Monday, 15 August 2016

elementary set theory - Prove F(F1(B))=B for onto function

Suppose that f:XY is an onto function. Prove that for all subsets B subset of Y, f(f1(B))=B. I don't know how to do this if the function is not also one to one, which it is not. Any help proving this would be greatly appreciated.

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real analysis - How to find limhrightarrow0fracsin(ha)h

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