设f(x)在x=0处可导,且对任意x.y满足f(x+y)=f(x)f(y),证明f(x)处处可导,且

问题描述:

设f(x)在x=0处可导,且对任意x.y满足f(x+y)=f(x)f(y),证明f(x)处处可导,且
f'(x)=f'(0)f(x)

f(0+0)=f(0)*f(0),则f(0)=0或1,当f(0)=0时,f(x)==0;
f(0)=1,则x趋于0时,极限(f(x)-1)/x存在=f'(0),在任一点x0处,当a趋于0时,极限
[f(x0+a)-f(x0)]/a=f(x0)[f(a)-1]/a=f(x0)f'(0).