Question

先化简，再求值：[(xy+2)(xy-2)-2(x²y²-2)]÷xy,其中x=10,y=-1/25

Answer 1

[xy²-4-2x²y²+4]/xy
=[xy²-2x²y²]/xy
=xy-2xy
=-xy
当x=10，y=-1/25时
原式=-（10*-1/25）
=2/5

Answer 2

[(xy+2)(xy-2)-2(x²y²-2)]÷xy
=[x^2y^2-4-2x^2y^2+4]/(xy)
=-x^2y^2/(xy)
=-xy
=-10*(-1/25)
=2/5
,其中x=10,y=-1/25