vector{AD}=4*vector{BС}
значит
vector{a}+4*vector{BC}-vector{b}-vector{BC}=0 ⇒ 3*vector{BC}=vector{b}-vector{a} ⇒
[b]vector{BC}=(1/3)vector{b}-(1/3)vector{a} [/b]
vector{CO}+vector{OD}+vector{DC}=0
[b]vector{OD}[/b]=(7/9) vector=(7/9)*4*vector{BС}=(28/9)vector{BС}=[b](28/27)vector{b}-(28/27)vector{a}[/b]
значит
[b]vector{CO}[/b]=-vector{OD}-vector{DC}=-(28/27)vector{b}+(28/27)vector{a}-vector{b}=[b]-(55/27)vector{b}+(28/27)vector{a}[/b]