[(xy-2)(-xy-2)-4(xy-1)^2]除以(-xy),其中x=20,y=-25分之1

题目

[(xy-2)(-xy-2)-4(xy-1)^2]除以(-xy),其中x=20,y=-25分之1

答案

[(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=-...