Let $f(x) = |x-3|$. Evaluate the following limits.

$\displaystyle \lim_{x\to 3^-} \frac{f(x)-f(3)}{x-3}=$

$\displaystyle \lim_{x\to 3^+} \frac{f(x)-f(3)}{x-3}=$

Thus the function $f(x)$ is not differentiable at 3.