\[x^{2} + 5x + 6\]
\[D = 5^{2} - 4 \cdot 1 \cdot 6 = 25 - 24 = 1\]
\[x_{1} = \frac{- 5 + \sqrt{1}}{2} = \frac{- 5 + 1}{2} = \frac{- 4}{2} =\]
\[= - 2\]
\[x_{2} = \frac{- 5 - \sqrt{1}}{2} = \frac{- 5 - 1}{2} = \frac{- 6}{2} =\]
\[= - 3\]
\[x^{2} + 5x + 6 = (x + 2)(x + 3).\]