[4(xy-1)^2-(xy+2)(2-xy)]1/4xy =[4(x²y²-2xy+1)-(4-x²y²)]1/4xy =(4x²y²-8xy+4-4+x²y²)1/4xy =(5x²y²-8xy)1/4xy =(5xy-8)1/4x²y² ∵x=-2,y=1/2 ∴xy=-1 原式=(-5-8)1/4(-1)² =-13/4,1,
