Chapter 8.7, Problem 105E

(a)

To determine

To prove: $\underset{h\to 0}{\lim }\frac{f\left(x+h\right)-f\left(x-h\right)}{2h}=f\text{'}\left(x\right)$.

(b)

To determine

To prove: Explain the result $\underset{h\to 0}{\lim }\frac{f\left(x+h\right)-f\left(x-h\right)}{2h}=f\text{'}\left(x\right)$ graphically.