\[x^{2} - 8x - 209 = 0\]
\[D = ( - 8)^{2} - 4 \cdot 1 \cdot ( - 209) =\]
\[= 64 + 836 = 900;\ \ \ \sqrt{D} = 30.\]
\[x_{1} = \frac{8 + 30}{2} = \frac{38}{2} = 19;\ \ \ \ \ \]
\[\text{\ \ \ }x_{2} = \frac{8 - 30}{2} = \frac{- 22}{2} = - 11\]
\[Ответ:19;\ - 11.\]