\[\boxed{\mathbf{1499}\mathbf{.}}\]
\[y = x^{3} - x^{2} - 7x + 6;\]
\[касательная\ в\ M(2;\ - 4):\]
\[y^{'}(x) = \left( x^{3} \right)^{'} - \left( x^{2} \right)^{'} - (7x - 6)^{'} =\]
\[= 3x^{2} - 2x - 7;\]
\[k = y^{'}(2) = 3 \bullet 2^{2} - 2 \bullet 2 - 7 =\]
\[= 12 - 4 - 7 = 1.\]
\[Угол\ между\ касательной\ и\ \]
\[осью\ Ox:\]
\[a = arctg\ k = arctg\ 1 = \frac{\pi}{4}.\]
\[Ответ:\ \ a = \frac{\pi}{4}\text{.\ }\]