Question

Find the equation (in terms of ) of the line through the points (-4,5) and (1,-1)
y =?

Answer 1

`(\stackrel{x_1}{-4}~,~\stackrel{y_1}{5})\qquad (\stackrel{x_2}{1}~,~\stackrel{y_2}{-1}) ~\hfill \stackrel{slope}{m}\implies \cfrac{\stackrel{rise} {\stackrel{y_2}{-1}-\stackrel{y1}{5}}}{\underset{run} {\underset{x_2}{1}-\underset{x_1}{(-4)}}}\implies \cfrac{-6}{1+4}\implies -\cfrac{6}{5}`

`\begin{array}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}{-\cfrac{6}{5}}(x-\stackrel{x_1}{(-4)}) \implies y-5=-\cfrac{6}{5}(x+4) \\\\\\ y-5=-\cfrac{6}{5}x-\cfrac{24}{5}\implies y=-\cfrac{6}{5}x-\cfrac{24}{5}+5\implies y=-\cfrac{6}{5}x+\cfrac{1}{5}`