`P=(\frac{2\sqrt{a}}{\sqrt{a}+3}+\frac{\sqrt{a}}{\sqrt{a}-3}+\frac{3a+3}{9-a}):(\frac{2\sqrt{a}-2}{\sqrt{a}-3}-1)`
`ĐKXĐ:{(\sqrt{a}-3\ne0),(\sqrt{a}+3\ne0(luôn đúng)),(a>=0):}`
`<=>{(a\ne9),(a>=0):}`
`=(\frac{2\sqrt{a}(\sqrt{a}-3)+\sqrt{a}(\sqrt{a}+3)-3a-3}{(\sqrt{a}-3)(\sqrt{a}+3)}):(\frac{2\sqrt{a}-2-\sqrt{a}+3}{\sqrt{a}-3})`
`=(\frac{2a-6\sqrt{a}+a+3\sqrt{a}-3a-3}{(\sqrt{a}-3)(\sqrt{a}+3)}).\frac{\sqrt{a}-3}{\sqrt{a}+1}`
`=\frac{(-3\sqrt{a}-3)(\sqrt{a}-3)}{(\sqrt{a}-3)(\sqrt{a}+3)(\sqrt{a}+1)}`
`=\frac{-3}{\sqrt{a}+3}`
`b)P<-2/5`
`<=>\frac{-3}{\sqrt{a}+3}<-2/5`
`<=>\frac{-3}{\sqrt{a}+3}+2/5<0`
`<=>\frac{-15+2\sqrt{a}+6}{5\sqrt{a}+15}<0`
`<=>\frac{2\sqrt{a}-9}{5\sqrt{a}+15}<0`
Vì `5\sqrt{a}+15>0`
`<=>2\sqrt{a}-9<0`
`<=>2\sqrt{a}<9`
`<=>\sqrt{a}<9/2`
`<=>a<81/4`
Vậy `a<81/4` thì `P<-2/5`
`c)\frac{-3}{\sqrt{a}+3}`
Vì `\sqrt{a}+3>=3`
`->\frac{-3}{\sqrt{a}+3}>=-1`
Dấu "=" xảy ra khi `\sqrt{a}+3=3<=>a=0`
Vậy `GTNNNN=-1` khi và chỉ khi `a=0`
