Ta có: 3→BI=2→CI3BI→=2CI→
⇒→BI→CI=23⇒BI→CI→=23
⇒→BI→CI+→IB=→BI→CI−→BI=23−1=2⇒BI→CI→+IB→=BI→CI→−BI→=23−1=2
⇒BI→CB=2⇒BICB→=2
⇒→BI=2→CB⇒BI→=2CB→
Ta có: →AI=→AC+→CI=→AC+→CB+→BIAI→=AC→+CI→=AC→+CB→+BI→
=→AC+→CB+2→CB=AC→+CB→+2CB→
=→AC+3→CB=AC→+3CB→
=→AC+3(→CA+→AB)=AC→+3(CA→+AB→)
=→AC+3→CA+3→AB=AC→+3CA→+3AB→
=→AC−3→AC+3→AB=AC→−3AC→+3AB→
=−2→AC+3→AB=−2AC→+3AB→
→CI=3→BI2=3.2→BC2=3→BCCI→=3BI→2=3.2BC→2=3BC→
Ta có: →AJ=→AB+→BJ=→AB−→JBAJ→=AB→+BJ→=AB→−JB→
=→AB−2→IC5=→AB+2→CI5=AB→−2IC→5=AB→+2CI→5
=→AB+2.3.→BC5=AB→+2.3.BC→5
=→AB+65(→BA+→AC)=AB→+65(BA→+AC→)
=−15→AB+65→AC