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

问题描述:

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

[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