[tex]\bf \begin{array}{ccccccccc}
&&x_1&&y_1&&x_2&&y_2\\
% (a,b)
&&(~ 9 &,& 2~)
% (c,d)
&&(~ 3 &,& -8~)
\end{array}
\\\\\\
% slope = m
slope = m\implies
\cfrac{\stackrel{rise}{ y_2- y_1}}{\stackrel{run}{ x_2- x_1}}\implies \cfrac{-8-2}{3-9}\implies \cfrac{-10}{-6}\implies \cfrac{5}{3}[/tex]
