1
[exo:suprou8] Montrer que : (\(g\circ f\;\mbox{injective}\Rightarrow f\;\mbox{injective}\)) et (\(g\circ f\;\mbox{surjective}\Rightarrow g\;\mbox{surjective}\)).
[exo:suprou8] Montrer que : (\(g\circ f\;\mbox{injective}\Rightarrow f\;\mbox{injective}\)) et (\(g\circ f\;\mbox{surjective}\Rightarrow g\;\mbox{surjective}\)).