well, the line that contains those points will more or less look like the one in the picture below, and we can use any two points from that set to get its slope, say hmmmmm let's use (-5,7) and (1,-2)
[tex](\stackrel{x_1}{-5}~,~\stackrel{y_1}{7})\qquad (\stackrel{x_2}{1}~,~\stackrel{y_2}{-2}) \\\\\\ \stackrel{slope}{m}\implies \cfrac{\stackrel{rise} {\stackrel{y_2}{-2}-\stackrel{y1}{7}}}{\underset{run} {\underset{x_2}{1}-\underset{x_1}{(-5)}}}\implies \cfrac{-9}{1+5}\implies \cfrac{-9}{6}\implies -\cfrac{3}{2}[/tex]
