21.設(shè)函數(shù)f(x)=lnx-
-bx
(Ⅰ)當(dāng)a=b=
時(shí),求函數(shù)f(x)的單調(diào)區(qū)間;
(Ⅱ)令F(x)=f(x)+
<x≤3),其圖象上任意一點(diǎn)P(x
0,y
0)處切線的斜率k≤
恒成立,求實(shí)數(shù)a的取值范圍;
(Ⅲ)當(dāng)a=0,b=-1時(shí),方程f(x)=mx在區(qū)間[1,e
2]內(nèi)有唯一實(shí)數(shù)解,求實(shí)數(shù)m的取值范圍.