Rút gọn biểu thức P

$\mathrm{Cho} \mathrm{biểu} \mathrm{thức}: \mathrm{P}=$$\frac{2\sqrt{\mathrm{x}}+3}{\sqrt{\mathrm{x}}-3}+$$\frac{\sqrt{\mathrm{x}}+3}{4-\sqrt{\mathrm{x}}}$$-\frac{x-6\sqrt{x}}{\left(\sqrt{x}-3\right)\left(\sqrt{x}-4\right)}$$\mathrm{với} \mathrm{x}\ge 0; \mathrm{x}$$\ne$$9; \mathrm{x}$$\ne$$16.$

$$\begin{gathered} \mathrm{a}) \mathrm{Rút} \mathrm{gọn} \mathrm{biểu} \mathrm{thức} \mathrm{P}. \\ \mathrm{b}) \mathrm{Tìm} \mathrm{x} \mathrm{để} \mathrm{P}=2. \end{gathered}$$