f(x)=(1+2lnx)/x
定义域x>0
对函数求导
df/dx=(2/x*x-(1+2lnx))/x^2=(1-2lnx)/x^2
另1-2lnx=0,得x=e^(1/2)
函数在区间（a,a+1）上存在极值,则
ae^(1/2),得
e^(1/2)-1