vec to khong ghi dc tat ca dieu co vectoMA-MB=BA<=>MA-MB=BM+MA<=>MA-MA-MB+BM =0 (BM=-MB)<=>0=0(dung voi moiM)MA-MB=AB<=>MA-MB=AM+MB<=>2(MA-MB)=0<=>MA=MBmoiM deu khong thoa MA+MB=0<=>MA=BMMlatrung diem doan AB
xzzcc→
vec
to khong ghi dc
tat ca dieu co vectoMA-MB=BA<=>MA-MB=BM+MA<=>MA-MA-MB+BM =0 (BM=-MB)<=>0=0(dung voi moiM)MA-MB=AB<=>MA-MB=AM+MB<=>2(MA-MB)=0<=>MA=MBmoiM deu khong thoa MA+MB=0<=>MA=BMMlatrung diem doan AB