若x
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若x
若x
若x
(x^2+y^2)(x-y)-(x^2-y^2)(x+y)=(x^2+y^2)(x-y)-(x+y)^2(x-y)=(x-y)(x^2+y^2-(x+y)^2)=(x-y)(-2xy)=2xy(y-x)>0
(x^2+y^2)(x-y)>(x^2-y^2)(x+y)
若x
若x
若x
(x^2+y^2)(x-y)-(x^2-y^2)(x+y)=(x^2+y^2)(x-y)-(x+y)^2(x-y)=(x-y)(x^2+y^2-(x+y)^2)=(x-y)(-2xy)=2xy(y-x)>0
(x^2+y^2)(x-y)>(x^2-y^2)(x+y)