[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
