a) Điều kiện xác định:
$\left\{ \begin{array}{l}2-\sqrt[]{x}\neq 0\\2+\sqrt[]{x}\neq 0\end{array} \right.$
$⇔ 2-\sqrt[]{x}\neq 0$
$⇔ \sqrt[]{x}\neq 2$
$⇒ \left\{ \begin{array}{l}x≥0\\x\neq 4\end{array} \right.$
b) $P=\Bigg(\dfrac{8-x\sqrt[]{x}}{2-\sqrt[]{x}}+2\sqrt[]{x}\Bigg)\Bigg(\dfrac{2-\sqrt[]{x}}{2+\sqrt[]{x}}\Bigg)^2$
$=\Bigg(\dfrac{(2-\sqrt[]{x})(4+2\sqrt[]{x}+x)}{2-\sqrt[]{x}}+2\sqrt[]{x}\Bigg)\Bigg(\dfrac{2-\sqrt[]{x}}{2+\sqrt[]{x}}\Bigg)^2$
$=(x+4\sqrt[]{x}+4)\Bigg(\dfrac{2-\sqrt[]{x}}{2+\sqrt[]{x}}\Bigg)^2$
$=(\sqrt[]{x}+2)^2.\Bigg(\dfrac{2-\sqrt[]{x}}{2+\sqrt[]{x}}\Bigg)^2$
$=(\sqrt[]{x}-2)^2$
