Geometrija + vektoriai. Need help :(

http://img22.imageshack.us/i/1234ub.jpg/
13uzd. 2,3. 

nulis minciu :/

2. OA=OE+EA=1/3BE+EA=1/3(AE-AB)+1/2CA=
=1/3(1/2AC-AB)+1/2CA=1/6AC-1/3AB-1/2AC=-1/3AC-1/3AB=-1/3b-1/3c

3. OD=OB+BD=2/3EB+1/2BC=2/3(AB-AE)+1/2(AC-AB)=
=2/3AB-2/3AE+1/2AC-1/2AB=1/6AB-2/3(1/2AC)+1/2AC=
=1/6AB-1/3AC+1/2AC=1/6AB+1/6AC=1/6c+1/6b

Didelis, didelis aciu :)