解5(3a²b-ab²)-4(-ab²+3a²b)=(15a²b-12a²b)+(-5ab²+4ab²)=3a²b-ab²=ab(3a-b)=1/2×(-1/3)(3×1/2+1/3)=-1/6×(3/2+1/3)=-1/6×11/6=-11/36
