2. $A=\dfrac{x^4-16}{x^4-4x^3+8x^2-16x+16}=\dfrac{(x-2)(x+2)(x^2+4)}{(x-2)^2(x^2+4)}=\dfrac{x+2}{x-2}=1+\dfrac{4}{x-2}$Do đó $A \in \mathbb Z \Leftrightarrow \dfrac{4}{x-2} \in \mathbb Z \Leftrightarrow x-2 \in \left\{ {-1,1,-2,2,-4,4} \right\} \Leftrightarrow x \in \left\{ {1,3,0,4,-2,6} \right\}$
2. $A=\dfrac{x^4-16}{x^4-4x^3+8x^2-16x+16}=\dfrac{(x-2)(x+2)(x^2+4)}{(x-2)(x^2+4)}=\dfrac{x+2}{x-2}=1+\dfrac{4}{x-2}$Do đó $A \in \mathbb Z \Leftrightarrow \dfrac{4}{x-2} \in \mathbb Z \Leftrightarrow x-2 \in \left\{ {-1,1,-2,2,-4,4} \right\} \Leftrightarrow x \in \left\{ {1,3,0,4,-2,6} \right\}$
2. $A=\dfrac{x^4-16}{x^4-4x^3+8x^2-16x+16}=\dfrac{(x-2)(x+2)(x^2+4)}{(x-2)
^2(x^2+4)}=\dfrac{x+2}{x-2}=1+\dfrac{4}{x-2}$Do đó $A \in \mathbb Z \Leftrightarrow \dfrac{4}{x-2} \in \mathbb Z \Leftrightarrow x-2 \in \left\{ {-1,1,-2,2,-4,4} \right\} \Leftrightarrow x \in \left\{ {1,3,0,4,-2,6} \right\}$