f'(x)=-lnx/x^2+1/x^2=(1-lnx)/x^2
f'(x)=0
1-lnx=0
lnx=1
x=e
當(dāng)x
當(dāng)x>e時(shí),f'(x)<0,函數(shù)為減函數(shù)
分?jǐn)?shù)線下為xlnx
f'(x)=-1/(xlnx)^2*(lnx+1)=-(lnx+1)/(xlnx)^2
f'(x)=0
1+lnx=0
lnx=-1
x=1/e
當(dāng)x<1/e時(shí),f'(x)>0,函數(shù)為增函數(shù)
當(dāng)x>1/e時(shí),f'(x)<0,函數(shù)為減函數(shù)