\[\boxed{\mathbf{749\ (749).\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\ x² - 7x + 10 =\]
\[= \left( x^{2} - 4x + 4 \right) - 3x + 6 =\]
\[= (x - 2)^{2} - 3 \cdot (x - 2) =\]
\[= (x - 2)(x - 2 - 3) =\]
\[= (x - 2)(x - 5)\]
\[2)\ y² + 3y - 4 =\]
\[= \left( y^{2} + 8y + 16 \right) - 5y - 20 =\]
\[= (y + 4)^{2} - 5 \cdot (y + 4) =\]
\[= (y + 4)(y + 4 - 5) =\]
\[= (y + 4)(y - 1)\]
\[3)\ a² + 8a + 12 =\]
\[= \left( a^{2} + 4a + 4 \right) + 4a + 8 =\]
\[= (a + 2)^{2} + 4 \cdot (a + 2) =\]
\[= (a + 2)(a + 2 + 4) =\]
\[= (a + 2)(a + 6)\]
\[4)\ x² - x - 6 =\]
\[= \left( x^{2} - 6x + 9 \right) + 5x - 15 =\]
\[= (x - 3)^{2} + 5 \cdot (x - 3) =\]
\[= (x - 3)(x - 3 + 5) =\]
\[= (x - 3)(x + 2)\]