原式=(-1/2)³▪(x²)³▪y³+(0.5)²▪x²▪y³▪(x²)²
=(-1/8)x^6▪y³+1/4x²▪y³▪x^4
=(-1/8)x^6▪y³+1/4x^6▪y³
=1/8x^6▪y³