y=(x^2+3)/(√x^2+2) 求最小值
问题描述：
y=(x^2+3)/(√x^2+2) 求最小值
答
y=(x^2+3)/(√x^2+2)=(x^2+2)/(√x^2+2)+1/(√x^2+2)=(√x^2+2)+1/(√x^2+2)
令u=(√x^2+2),注意到u>=√2,0=√2+1/√2=(3√2)/2