化简求值(xy-x²)/xy分之x²-2xy+y²乘x²分之x-y,其中y=二分之一

化简求值(xy-x²)/xy分之x²-2xy+y²乘x²分之x-y,其中y=二分之一

(xy-x²)÷(x²-2xy+y²)/(x-y)×(x-y)/x²
=-x(x-y)÷(x-y)²/x²
=-x(x-y)×x²/(x-y)²
=-x³/(x-y)
∵x=3/2,y=1/2
∴-x³/(x-y)=-(3/2)³/(3/2-1/2)=-(3/2)³=-27/8