میدانیم شیب خط گذرنده از $A\left| \begin{gathered}
{x_1} \hfill \\
{y_1} \hfill \\
\end{gathered} \right.$ و $B\left| \begin{gathered}
{x_2} \hfill \\
{y_2} \hfill \\
\end{gathered} \right.$ برابر است با:
$a = \frac{{{y_2} - {y_1}}}{{{x_2} - {x_1}}}$
$ \Rightarrow - \frac{4}{7} = \frac{{a + 2 - \frac{2}{3}a}}{{\frac{1}{2}a - 3 - (2a - 5)}} \Rightarrow - \frac{4}{7} = \frac{{\frac{1}{3}a + 2}}{{ - \frac{3}{2}a + 2}} \Rightarrow $
$ - 4( - \frac{3}{2}a + 2) = 7(\frac{1}{3}a + 2) \Rightarrow 6a - 8 = \frac{7}{3}a + 14 \to \frac{{11}}{3}a = 22$
$ \to a = \frac{{\frac{{22}}{1}}}{{\frac{{11}}{3}}} = \frac{{3 \times 22}}{{11}} = 6$