OC=OA+AC=OA+1/3AB=OA+1/3 (OB -OA)= 2/3OA +1/ 3 OB=2/3×3a +1/3×3 b=2a+b
OD=OA + AD =OA+2/3 AB =OA+2/3( OB - OA )= 1/3 OA + 2/3OB= 1/3×3a +2/3×3b=
a+2b
但既然是向量,请注意向量的表示方法OA,OB等头上带→,电脑不太好打,
OC=OA+AC=OA+1/3AB=OA+1/3 (OB -OA)= 2/3OA +1/ 3 OB=2/3×3a +1/3×3 b=2a+b
OD=OA + AD =OA+2/3 AB =OA+2/3( OB - OA )= 1/3 OA + 2/3OB= 1/3×3a +2/3×3b=
a+2b
但既然是向量,请注意向量的表示方法OA,OB等头上带→,电脑不太好打,