ThmDex – An index of mathematical definitions, results, and conjectures.
Result R1131 on D528: Map image
Image of inverse image
Formulation 2
Let $f : X \to Y$ be a D18: Map.
Then
(1) $f(f^{-1} B) \subseteq B$ for all $B \subseteq Y$
(2) $f(f^{-1} B) = B$ for all $B \subseteq Y$ if and only if $f$ is a D466: Surjective map