Suppose I know that [tex]x\in A \Leftrightarrow f(x)\in A[/tex]. Can someone explain why I know, on the strength of this, that [tex]f(A) \subseteq A[/tex] and [tex]f^{-1}(A) \subseteq A[/tex]?(adsbygoogle = window.adsbygoogle || []).push({});

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# Basic (I think) image/preimage questions

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