f(x)=2x+1∕x定义域{x|x≠0}f(x)为奇函数当x>0时f(x)≥2√2x*(1/x)=2√2当且仅当2x=1/x即x=1/√2等号成立当x<0,则-x>0f(-x)=-2x-(1/x)≥2√(-2x)*(-1/x)=2√2当且仅当2x=1/x即x=-1/√2,等号成立f(x)=-f(-x)≤-2√2f(x)值域{y|y≤-2√2或y≥2√2}
