Explicație pas cu pas:
[tex] \bf a) \: (ABC) \: \cap \: (ABD) = \green{AB}[/tex]
[tex]\bf b) \: (ABC) \: \cap \: (ACD) = \blue{AC}[/tex]
[tex]\bf c) \: (ABC) \: \cap \: (BCD) = \purple{BC}[/tex]
[tex]\bf d) \: AB\subset \red{(ABC)}\:\: si \:\: AB \subset \red{(ABD)}[/tex]
