当x=0时, (0+h)-ln(1+0) ∫"(0)=lim h→>0 f(0)=lim ln[1+(0+h)-In(1+0) h f∫(0)=1. 1,x≤0 f'(x)={1 1+,>0当x = 0时, h h f h (0 ) ln(1 0) (0) lim 0 + − +  = → − − = 1, h h f h ln[1 (0 )] ln(1 0) (0) lim 0 + + − +  = + → + = 1,  f (0) = 1. . , 0 1 1 1, 0 ( )      +    = x x x f x