21.已知e是自然對(duì)數(shù)的底數(shù),函數(shù)f(x)=
與F(x)=f(x)-x+
的定義域都是(0,+∞).
(1)求函數(shù)f(x)在點(diǎn)(1,f(1))處的切線方程;
(2)判斷函數(shù)F(x)零點(diǎn)個(gè)數(shù)
(3)用min{m,n}表示m,n的最小值,設(shè)x>0,g(x)=min{f(x),x-
},若函數(shù)h(x)=g(x)-cx
2在(0,+∞)上為增函數(shù),求實(shí)數(shù)c的取值范圍.