\(\begin{array}{l}
Bai\,2)\\
1)\, = 5xy\left( {3x + 4y - 5} \right)\\
2)\, = {\left( {y - 1} \right)^2}\\
3)\, = {\left( {x + 3} \right)^3}\\
4)\, = {2^3} - {\left( {3x} \right)^3} = \left( {2 - 3x} \right)\left( {4 + 6x + 9{x^2}} \right)\\
5)\, = \left( {1 - 2x} \right)\left( {1 + 2x} \right)\\
6)\, = \left( {x + y + 5} \right)\left( {x + y - 5} \right)\\
7)\, = 4x\left( {x + 2y} \right) - 3\left( {x + 2y} \right)\\
= \left( {4x - 3} \right)\left( {x + 2y} \right)\\
8)\, = {x^2}\left( {2 - z} \right) + {y^2}\left( {2 - z} \right) - \left( {2 - z} \right)\\
= \left( {2 - z} \right)\left( {{x^2} + {y^2} - 1} \right)\\
9)\, = 3\left( {{x^2} - 2xy + {y^2}} \right) = 3{\left( {x - y} \right)^2}\\
10)\, = {\left( {x - y} \right)^2} - {4^2}\\
= \left( {x - y - 4} \right)\left( {x - y + 4} \right)\\
11)\, = a\left( {{y^2} - 4y + 4} \right) - b\left( {{y^2} - 4y + 4} \right)\\
= \left( {a - b} \right){\left( {y - 2} \right)^2}\\
12)\, = 2\left( {{x^2} + 14x + 49 - 4{y^2}} \right)\\
= 2\left[ {{{\left( {x + 7} \right)}^2} - {{\left( {2y} \right)}^2}} \right]\\
= 2\left( {x + 7 + 2y} \right)\left( {x + 7 - 2y} \right)
\end{array}\)