Vì:`\sqrt{2(x-2)}=\sqrt{2}[(\sqrt{x})^2-(\sqrt{2})^2]=\sqrt{2}(\sqrt{x}-\sqrt{2})(\sqrt{x}+\sqrt{2})`
`⇒` Chỗ bạn hỏi thiếu `\sqrt{x}+\sqrt{2}` nhé.
`P=\frac{\sqrt{2(x-2)}}{x-2}`
`=\frac{\sqrt{2(x-2)}}{(\sqrt{x}+\sqrt{2})(\sqrt{x}-\sqrt{2})`
`=\frac{\sqrt{2}(\sqrt{x}-\sqrt{2})(\sqrt{x}+\sqrt{2})}{(\sqrt{x}+\sqrt{2})(\sqrt{x}-\sqrt{2})`
`=\sqrt{2}`
