\[x^{2} + 6x + 8\]
\[D = 6^{2} - 4 \cdot 1 \cdot 8 = 36 - 32 = 4\]
\[x_{1} = \frac{- 6 + \sqrt{4}}{2} = \frac{- 6 + 2}{2} = \frac{- 4}{2} =\]
\[= - 2\]
\[x_{2} = \frac{- 6 - \sqrt{4}}{2} = \frac{- 6 - 2}{2} = \frac{- 8}{2} =\]
\[= - 4\]
\[x^{2} + 6x + 8 = (x + 2)(x + 4).\]