Answer
a) $\frac{\Delta y}{\Delta x}=\frac{f(x)-f(3)}{x-3}$
b) $\lim\limits_{x \to 3}=\frac{f(x)-f(3)}{x-3}$
Work Step by Step
a) $\frac{\Delta y}{\Delta x}=\frac{f(x)-f(3)}{x-3}$
b) Use the standard formula for slope of tangent $\lim\limits_{x \to 3}=\frac{f(x)-f(3)}{x-3}$
