$P=\dfrac{4}{\sqrt{x}-1}+\dfrac{3}{\sqrt{x}-1}-\dfrac{6}{\sqrt{x}+2}$ ĐK: $x>0;x\neq1$
$P=\dfrac{7}{\sqrt{x}-1}-\dfrac{6}{\sqrt{x}+2}$
$P=\dfrac{7(\sqrt{x}+2)-6(\sqrt{x}-1)}{(\sqrt{x}-1)(\sqrt{x}+2)}$
$P=\dfrac{7\sqrt{x}+14-6\sqrt{x}+6}{(\sqrt{x}-1)(\sqrt{x}+2)}$
$P=\dfrac{\sqrt{x}+20}{(\sqrt{x}-1)(\sqrt{x}+2)}$
Vậy $P=\dfrac{\sqrt{x}+20}{(\sqrt{x}-1)(\sqrt{x}+2)}$
$R=(\dfrac{1}{\sqrt{x}-1}-\dfrac{\sqrt{x}}{x-1}):\dfrac{1}{\sqrt{x}+1}$ ĐK: $x>0;x\neq1$
$R=(\dfrac{1}{\sqrt{x}-1}-\dfrac{\sqrt{x}}{(\sqrt{x}-1)(\sqrt{x}+1)}).(\sqrt{x}+1)$
$R=\dfrac{\sqrt{x}+1-\sqrt{x}}{(\sqrt{x}-1)(\sqrt{x}+1)}.(\sqrt{x}+1)$
$R=\dfrac{1}{\sqrt{x}-1}$
Vậy $R=\dfrac{1}{\sqrt{x}-1}$ với $x>0;x\neq1$
