D = \(\sqrt{(x+y)^2 - 82z} + \sqrt{\frac{1.2x^2 - f(x^2+3)}{2z^2}}\) a) \( R \subset D \) b) \( \text{Tìm } x \in \mathbb{Z} \text{ để } D \in \mathbb{Z} \)

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D = \(\sqrt{(x+y)^2 - 82z} + \sqrt{\frac{1.2x^2 - f(x^2+3)}{2z^2}}\)

a) \( R \subset D \)

b) \( \text{Tìm } x \in \mathbb{Z} \text{ để } D \in \mathbb{Z} \)