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

题目

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

答案

(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...