先化简 再求值:[4(xy-1)^2-(xy+2)(2-xy)]1/4xy,其中x=-2,y=1/5
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=1/5
答
[4(xy-1)^2-(xy+2)(2-xy)]1/4xy=[4(xy-1)^2 +(xy+2)(xy-2)]1/4xy=[4(xy)²-8(xy)+4+(xy)²-4]÷(4xy)=[5(xy)²-8(xy)]÷(4xy)=(5xy-8)/4已知x=-2,y=1/5,那么：xy=-2/5所以：原式=(5xy-8)/4=[5*(-2/5)-8]...