1、f(x)=x+2/x令x1>x2>1f(x1)-f(x2)=x1+2/x1-x2-2/x2=(x1-x2)+2/x1-2/x2=[x1x2(x1-x2)+2x2-2x1]/x1x2=(x1x2-2)(x1-x2)/x1x2显然x1x2>0,x1-x2>0就看x1x2-2的符号则x>√2,时,x1x2>2,10,f(x1)>f(x2),增函数1...