化简求值；(xy-2²）÷x²-2xy+y²/xy×x²-y²/x²,其中x=-1/2,y=-2/3.

Question

化简求值；(xy-2²）÷ x²-2xy+y²/xy × x²-y²/x²,其中x=-1/2,y=-2/3.

Answer 1

原式=[-x(x-y)][xy/(x-y)²][(x+y)(x-y)/x²]
=-y(x+y)
=-7/9