6. The derivative of a function f at a number a denoted by f'(a), is f'(a) = lim f(ath) - f(a) h-0 h if this limit exists. Sketch f(r) = 12 and draw a representation that shows the relationship between f'(a), f(ath) and f(a). Explain how your illustration represents the definition of the derivative a function at a number a