化简求值y/x-y +y立方/x立方-2x平方y+xy平方除以xy+y平方/y平方-x平方,其中x=2/3,y=-3
问题描述：
化简求值y/x-y +y立方/x立方-2x平方y+xy平方除以xy+y平方/y平方-x平方,其中x=2/3,y=-3
答
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...