Giúp mik với ạ Phân tích các đa thức sau thành nhân tử: 1)4a^2b^4 - c^4d^2 2)100x^2 - (3x-y)^2 3)(a+b)^2 - (2a-b)^2 4)(3x+1)^2 - 4(x-2)^2

$$\eqalign{ & 1)\,\,4{a^2}{b^4} - {c^4}{d^2} \cr & = {\left( {2a{b^2}} \right)^2} - {\left( {{c^2}d} \right)^2} \cr & = \left( {2a{b^2} - {c^2}d} \right)\left( {2a{b^2} + {c^2}d} \right) \cr & 2)\,\,100{x^2} - {\left( {3x - y} \right)^2} \cr & = {\left( {10x} \right)^2} - {\left( {3x - y} \right)^2} \cr & = \left( {10x - 3x + y} \right)\left( {10x + 3x - y} \right) \cr & = \left( {7x + y} \right)\left( {13x - y} \right) \cr & 3)\,\,{\left( {a + b} \right)^2} - {\left( {2a - b} \right)^2} \cr & = \left( {a + b - 2a + b} \right)\left( {a + b + 2a - b} \right) \cr & = 3a\left( {2b - a} \right) \cr & 4)\,\,{\left( {3x + 1} \right)^2} - 4{\left( {x - 2} \right)^2} \cr & = {\left( {3x + 1} \right)^2} - {\left[ {2\left( {x - 2} \right)} \right]^2} \cr & = {\left( {3x + 1} \right)^2} - {\left( {2x - 4} \right)^2} \cr & = \left( {3x + 1 - 2x + 4} \right)\left( {3x + 1 + 2x - 4} \right) \cr & = \left( {x + 5} \right)\left( {5x - 3} \right) \cr} $$