3x²＋{-2分之3x＋3分之1y²}{2x-3分之2y}=3x²-3x²+2/3 xy²+xy-2/9 y³=2/3 xy²+xy-2/9 y³= -2/9×4/9-2/9-2/9×8/27= -2/9×(4/9 + 1 + 8/27)= -2/9×47/27= -94/243
