二阶可导指f'(x)导数存在。所以，f'(x)在x=2连续，f'(2)=e^(f(2))=e.用复合函数求导法则，f''(x)=e^(f(x))f'(x),所以f"(2)=e^(f(2))f'(2)=e*e=e^2
