jacky
问题补充说明：化简求值：(x-y+ X-y分之4xy)(x+y- x+y分之4xy),其中x=-2分之1，y=根号2.
x-y+(4xy)/(x-y)=[(x-y)²+4境对苗想明xy]/(x-y)=(x门船海粮运叶假血历+y)²/(x-y)
x+y-(4xy)/(x+y)=[(x+y)²-4xy]/(x+y)=(x-y)²/(x+y)
∴[x-y+(4xy)/(x-y)][x+y-(4xy空降威站金夫雨)/(x+y)]=(烧践乎绍重何征久移x+y)²/(x-y如)*(x-y)²/(x+y)=(x+y)(x-y)=x²-y²=(-1/2)²-(√2)²=1/亚夜门既引凯绍过4-2=-7/4
