\[\boxed{\text{718\ (718).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
Пояснение.
Решение.
\[\textbf{а)}\ x^{2} + 6x + 5 =\]
\[= x^{2} + 5x + x + 5 =\]
\[= x(x + 5) + (x + 5) =\]
\[= (x + 5)(x + 1)\]
\[\textbf{б)}\ x^{2} - x - 6 =\]
\[= x^{2} + 2x - 3x - 6 =\]
\[= x(x + 2) - 3 \cdot (x + 2) =\]
\[= (x + 2)(x - 3)\]
\[\textbf{в)}\ a^{2} - 5a + 4 =\]
\[= a^{2} - 4a - a + 4 =\]
\[= a(a - 4) - (a - 4) =\]
\[= (a - 4)(a - 1)\]
\[\textbf{г)}\ a^{2} - 6a - 16 =\]
\[= a^{2} - 8a + 2a - 16 =\]
\[= a(a - 8) + 2 \cdot (a - 8) =\]
\[= (a - 8)(a + 2)\]