先化简,再求值:[4(xy-1)^2-(xy+2)(2-xy)]÷(1/4xy),其中x=-2 y=1/4

问题描述:

先化简,再求值:[4(xy-1)^2-(xy+2)(2-xy)]÷(1/4xy),其中x=-2 y=1/4

原式=(4x²y²-8xy+4-4+x²y²)÷(1/4xy)
=(5x²y²-8xy)÷(1/4xy)
=20xy-32
=20*(-2)*(1/4)-32
=-10-32
=-42