[(xy-2)(-xy-2)-4(xy-1)^2]除以(-xy)
=[-x²y²+4-4(x²y²-2xy+1)]÷(-xy)
=(-x²y²+4-4x²y²+8xy-4)÷(-xy)
=(-5x²y²+8xy)÷(-xy)
=5xy-8
=5×20×（-25分之1 ）-8
=-4-8
=-12