利用基本不等式x+y>=2(xy)^(1/2) 有(a^2/b)^(1/2)+b^(1/2)>=2a^(1/2) (b^2/a)^(1/2)+a^(1/2)>=2b^(1/2)相加可得(a^2/b)^(1/2)+(b^2/a)^(1/2)+a^(1/2)+b^(1/2)>=2[a^(1/2)+b^(1/2)]所以(a^2/b)^(1/2)+(b^2/a)^(1/2)>=a^(1/2)+b^(1/2)
