例4求函数f(x)=a(a>0,≠1)的导数 x+h 解(a)=mh =a m h→0 =aIn a 即(ay=alna (e)=e 上页例 4 求函数 f (x) = a (a  0,a  1)的导数. x 解 h a a a x h x h x −  = + →0 ( ) lim h a a h h x 1 lim0 − = → a ln a . x =(a ) a ln a. x x 即  = ( ) . x x e  = e