Решите уравнение: (x-1)(x-2)+(x+4)(x-4)+3x=0.

\[2x² - 14 = 0\ \ \ |\ :2\]

\[x^{2} - 7 = 0\]

\[\left( x - \sqrt{7} \right)\left( x + \sqrt{7} \right) = 0\]

\[x - \sqrt{7} = 0,\ \ x + \sqrt{7} = 0\]

\[x = \sqrt{7}\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x = - \sqrt{7}\]

\[Ответ:\ x = - \sqrt{7};\ \ x = \sqrt{7}.\]