[tex]\bf M(\stackrel{x_1}{2}~,~\stackrel{y_1}{4})\qquad
N(\stackrel{x_2}{9}~,~\stackrel{y_2}{4})
\\\\\\
% slope = m
slope = m\implies
\cfrac{\stackrel{rise}{ y_2- y_1}}{\stackrel{run}{ x_2- x_1}}\implies \cfrac{4-4}{9-2}\implies \cfrac{0}{7}\implies 0
\\\\\\
% point-slope intercept
\stackrel{\textit{point-slope form}}{y- y_1= m(x- x_1)}\implies y-4=0(x-2)\implies y-4=0\implies y=4[/tex]
