\[\boxed{\text{999.}\text{\ }еуроки - ответы\ на\ пятёрку}\]
\[\textbf{а)}\ 16 - 9 \cdot (p + 3)^{2} =\]
\[= \left( 4 - 3 \cdot (p + 3) \right)\]
\[\left( 4 + 3 \cdot (p + 3) \right) =\]
\[= (4 - 3p - 9)(4 + 3p + 9) =\]
\[= ( - 5 - 3p)(13 + 3p)\]
\[\textbf{б)}\ 9 - 25 \cdot (4 - x)^{2} =\]
\[= \left( 3 - 5 \cdot (4 - x) \right)\]
\[\left( 3 + 5 \cdot (4 - x) \right) =\]
\[= (3 - 20 + 5x)(3 + 20 - 5x) =\]
\[= (5x - 17)(23 - 5x)\]
\[\textbf{в)}\ 1 - 36 \cdot (3y - 1)^{2} =\]
\[= \left( 1 - 6 \cdot (3y - 1) \right)\]
\[\left( 1 + 6 \cdot (3y - 1) \right) =\]
\[= (1 - 18y + 6)(1 + 18y - 6) =\]
\[= (7 - 18y)(18y - 5)\]
\[\textbf{г)}\ 4 - 9 \cdot (a + b)^{2} =\]
\[= \left( 2 - 3 \cdot (a + b) \right)\]
\[\left( 2 + 3 \cdot (a - b) \right) =\]
\[= (2 - 3a - 3b)(2 + 3a + 3b)\]