Question Number 161204 by mathocean1 last updated on 14/Dec/21
$${Soit}\:{f}:\:{E}\rightarrow{F}\:,\:{une}\:{application}. \\ $$$$\mathscr{P}\left({E}\right)\:{est}\:{l}'{ensemble}\:{des}\:{parties} \\ $$$${de}\:{E}. \\ $$$${Montrer}\:{que}\:{f}\:{est}\:{injective}\:\Leftrightarrow\:\forall\:{A}\:\in\:\mathscr{P}\left({E}\right),\:{A}\:\subset\:{f}^{−\mathrm{1}} \left({f}\left({A}\right)\right) \\ $$