原式=[y/(x-y)]+[y³/(x³-2x²y+xy²)]÷[(xy+y²)/(y²-x²)] =[y/(x-y)]+{y³/[x(x²-2xy+y²)]}÷{y(x+y)/[-(x-y)(x+y)]}=[y/(x-y)]+{y³/[x(x-y)²]}×[-(x-y...