\[\boxed{\mathbf{719\ (719).\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[2x^{2} - 7x - 13 = 0\]
\[x_{1} \cdot x_{2} - 4x_{1} - 4x_{2} =\]
\[= x_{1} \cdot x_{2} - 4 \cdot \left( x_{1} + x_{2} \right) =\]
\[= - \frac{13}{2} - 4 \cdot \left( \frac{7}{2} \right) =\]
\[= - \frac{13}{2} - \frac{28}{2} = - \frac{41}{2} = - 20,5.\]