I need some help on an exercise because i didn't really understand how to prove a statement like this :
let E and F be two sets and let be a map from E to F. Let A and A' be two subsets of E. Let B and B' be two subsets of F.
(AUA')=( (A)U (A'))
Can you please help me please? I know I have to demonstrate it but I don't know how...
Thanks a lot