[tex]\bf slope = \cfrac{rise}{run} \implies
\cfrac{{{ y_2}}-{{ y_1}}}{{{ x_2}}-{{ x_1}}}\implies \cfrac{f(x_2)-f(x_1)}{x_2-x_1}\leftarrow
\begin{array}{llll}
\textit{average rate}\\
\textit{of change}
\end{array}\\\\
-----------------------------\\\\
m(k)=5k^6+6k^2\qquad
\begin{cases}
x_1=2\\
x_2=-9
\end{cases}\implies \cfrac{m(-9)-m(2)}{-9-2}[/tex]