f(x)=2x+1/x+1=(2(x+1)-1)/(x+1)=2-1/(x+1)1<=x<=42<=x+1)<=5所以,1/5<=1/(x+1)<=1/2-1/2<=-1/(x+1)<=-1/53/2<=2-1/(x+1)<=9/5即最大值是9/5,最小值是3/2
最大为37/4最小为3
