令X2>X1>0,F(x)=2x+1/x^2=2/x+1/x^2
F(X2)-F(X1)=(2/X2+1/X2^2)-(2/X1+1/X1^2)
=(1/X2-1/X1)(2+1/X1+1/X2)
令F(X2)-F(X1)>0,则0