Let f:X->Y be a function(adsbygoogle = window.adsbygoogle || []).push({});

1) Given any subset B of Y, prove that f(f^-1(B)) is a subset of B

2) Prove that f(f^-1(B))=B for all subsets B of Y if and only if f is surjective

Help anybody?

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# Set Theory proofs

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