f'(x)=（e^ⅹ)′+(e^ⅹ)9′(x)=e^ⅹ[g′(ⅹ)+g(ⅹ)]

f′(ⅹ)=[e^(-ⅹ)]′g(x)+[e^(-ⅹ)]g′(ⅹ)=-[e^(-x)]g(ⅹ)+[e^(-x)]9′(x)=[e^(-ⅹ)][g′(ⅹ)+-g(ⅹ)]