Question Number 161205 by mathocean1 last updated on 14/Dec/21
$${Soit}\:{f}:\:{E}\rightarrow{F}\:{une}\:{application}.\: \\ $$$$\mathscr{P}\left({E}\right)\:{est}\:{l}'{ensemble}\:{des}\:{parties} \\ $$$${de}\:{E}.\:{Montrer}\:{que}: \\ $$$${f}\:{est}\:{surjective}\Leftrightarrow\forall\:{B}\:\in\:\mathscr{P}\left({E}\right),\:{f}\left({f}^{−\mathrm{1}} \left({B}\right)\right)={B}. \\ $$