to get the equation of any straight line all we need is two points, we have plenty there, hmmm say let's use hmmm (1 , 5) and hmmm (-3 , -7)
[tex](\stackrel{x_1}{1}~,~\stackrel{y_1}{5})\qquad (\stackrel{x_2}{-3}~,~\stackrel{y_2}{-7}) \\\\\\ \stackrel{slope}{m}\implies \cfrac{\stackrel{rise} {\stackrel{y_2}{-7}-\stackrel{y1}{5}}}{\underset{run} {\underset{x_2}{-3}-\underset{x_1}{1}}}\implies \cfrac{-12}{-4}\implies 3 \\\\\\ \begin{array}{|c|ll} \cline{1-1} \textit{point-slope form}\\ \cline{1-1} \\ y-y_1=m(x-x_1) \\\\ \cline{1-1} \end{array}\implies y-\stackrel{y_1}{5}=\stackrel{m}{3}(x-\stackrel{x_1}{1})\implies y-5=3x-3[/tex]
[tex]y=\stackrel{\stackrel{M}{\downarrow }}{3} x\stackrel{\stackrel{B}{\downarrow }}{+2}\qquad \impliedby \begin{array}{|c|ll} \cline{1-1} slope-intercept~form\\ \cline{1-1} \\ y=\underset{y-intercept}{\stackrel{slope\qquad }{\stackrel{\downarrow }{m}x+\underset{\uparrow }{b}}} \\\\ \cline{1-1} \end{array}[/tex]
