两边同时对x1求导,得
f'(x1+x2)=e^x1f(x2)+e^x2f'(x1)
另x1=x x2=0,得
f'(x)=f(x)+e^xf'(0)
注意到f'(0)=1,所以
f'(x)=e^(x+1)+f(x)