若x>y,xy=1,求证:(x2+y2)/(x-y)>= 二又根号二

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若x>y,xy=1,求证:(x2+y2)/(x-y)>=二又根号二若x>y,xy=1,求证:(x2+y2)/(x-y)>=二又根号二若x>y,xy=1,求证:(x2+y2)/(x-y)>=二又根号二左

若x>y,xy=1,求证:(x2+y2)/(x-y)>= 二又根号二
若x>y,xy=1,求证:(x2+y2)/(x-y)>= 二又根号二

若x>y,xy=1,求证:(x2+y2)/(x-y)>= 二又根号二
左边=[(x-y)^2+2xy]/(x-y)
=(x-y)+2/(x-y)>=2根号二------均值不等式,其中x-y>0

原式=(X^2+Y^2-2XY+2XY)/(X-Y)
=(X-Y)^2/(X-Y)+2XY/(X-Y)
=(X-Y)+2XY/(X-Y)
因为a+b>=2√ab
所以上式>=2√2xy
即 >=2√2