Em tách riêng từng bài để hỏi nhé
\(\begin{array}{l}
3)\,1)\, = 5a\left( {x + y} \right) + \left( {x + y} \right) = \left( {x + y} \right)\left( {5a + 1} \right)\\
2)\, = x\left( {2y - 1} \right) + y\left( {2y - 1} \right) = \left( {x + y} \right)\left( {2y - 1} \right)\\
3)\, = x\left( {a + b} \right) - y\left( {a + b} \right) = \left( {a + b} \right)\left( {x - y} \right)\\
4)\, = x\left( {x + y} \right) + a\left( {x + y} \right)\\
= \left( {x + a} \right)\left( {x + y} \right)\\
5)\, = c\left( {a + b} \right) + \left( {a + b} \right) = \left( {c + 1} \right)\left( {a + b} \right)\\
6)\, = 3\left( {a - b} \right) + x\left( {a - b} \right) = \left( {3 + x} \right)\left( {a - b} \right)\\
7)\, = \left( {a - b} \right)\left( {x + 1} \right)\\
8)\, = a\left( {x + y} \right) + 2\left( {x + y} \right) = \left( {a + 2} \right)\left( {x + y} \right)\\
9)\, = x\left( {x + y} \right) - 3\left( {x + y} \right) = \left( {x - 3} \right)\left( {x + y} \right)\,
\end{array}\)
