[tex]\bf (\stackrel{x_1}{1}~,~\stackrel{y_1}{1})\qquad
(\stackrel{x_2}{1}~,~\stackrel{y_2}{4})
\\\\\\
slope = m\implies
\cfrac{\stackrel{rise}{ y_2- y_1}}{\stackrel{run}{ x_2- x_1}}\implies \cfrac{4-1}{1-1}\implies \cfrac{3}{0}\impliedby und efined[/tex]
