1.57: Differentiating an Exponential Function

Given that

(a) show that

(b) Find an equation of the normal to the curve with equation $\displaystyle y=f(x)$ at the point on the curve where $\displaystyle x=0$.

Give your answer in the form $\displaystyle ax+by+c=0$, where $\displaystyle a$, $\displaystyle b$ and $\displaystyle c$ are integers.