a) \(=\dfrac{3x-7\sqrt{x}-6+2x-\sqrt{x}-3-9\sqrt{x}+15}{\left(\sqrt{x}-3\right)\left(\sqrt{x}+1\right)}=\dfrac{5\sqrt{x}-2}{\sqrt{x}=1}\)
b) \(x\ge0=>\sqrt{x}\ge0=>5\sqrt{x}\ge0=>5\sqrt{x}-2\ge-2=>P=\dfrac{5\sqrt{x}-2}{\sqrt{x}+1}\ge-2\)Vậy GTNN của \(P=-2\)