设P在y=x+1/x,(a,a+1/a)a>0则距离d=|3a-4a-4/a-1|/√(3²+4²)即分子要最小a>0a+4/a>=2√a*4/a=4所以a+4/a+1>=5|3a-4a-4/a-1|=|a+4/a+1|>=5所以d>=1当a=4/a取等号,a=2最小值是1,(2,5/2)...