Va rogg dau coroana clasă a5a ex 6

a) AB, BC, CD, DA, A`B`, B`C`, C`D`, D`A`, AC, BD, AC`, BD`, AD`, DA`, DC`, CD`, BC`, CB`, AB`, BA`.
b) (ABC), (A`B`C`), (ABB`), (BCC`), (DCC`), (ADD`), (ABC`), (ABD`), (A`BC), (BDC`), (A`BD).
Sper ca nu am ratat vreunul!