[tex]\bf (\stackrel{x_1}{-10}~,~\stackrel{y_1}{-8})\qquad (\stackrel{x_2}{-12}~,~\stackrel{y_2}{-7}) \\\\\\ \stackrel{slope}{m}\implies \cfrac{\stackrel{rise} {\stackrel{y_2}{-7}-\stackrel{y1}{(-8)}}}{\underset{run} {\underset{x_2}{-12}-\underset{x_1}{(-10)}}}\implies \cfrac{-7+8}{-12+10}\implies \cfrac{1}{-2}\implies -\cfrac{1}{2}[/tex]
