Gọi D(x;y). Ta có: 3vectoAD=(3x-6;3y-3); -2vectoBD=(-2x-2;-2y+4); vectoCD=(x-3;y-4). Theo bài ra: 3vectoAD-2vectoBD+vectoCD=vecto0 <=> $\left \{ {{3x-6-2x-2+x-3=0} \atop {3y-3-2y+4+y-4=0}} \right.$ <=>$\left \{ {{x=11/2} \atop {y=3/2}} \right.$ . Vậy D(11/2;3/2).