If $f : \mathbb{R} \to \mathbb{R}$, we can think of the derivative of $f$ at a point $x$, denoted $f'(x)$, as giving the slope of a line tangent to the graph of $f$ at the point $(x, f(x))$. One way to obtain the derivative is to consider a secant line through a second point $(x+h, f(x+h))$ on t...