`#Mon`
`a)ĐK:{(a>=0),(\sqrt{a}-3 \ne 0),(\sqrt{a}+3 \ne 0),(a-9 \ne 0):}`
`<=>{(a>=0),(a\ne 9),(c):}`
`Ta` `có:` `a=6\sqrt{2}+11`
`=3^2+2\sqrt{11}+\sqrt{2^2}+\sqrt{2^2}`
`=(3+\sqrt{2})^2`
`Khi` `đó:`
`A=\frac{\sqrt{(3+\sqrt{2})^2}+1}{\sqrt{(2+3)^2}-3}`
`=\frac{\sqrt{2}+3+1}{\sqrt{3}+3-3}`
`=\frac{4+\sqrt{2}}{\sqrt{2}}`
`=2\sqrt{2}+1`
`b)B=\frac{2\sqrt{a}}{\sqrt{a}+3}-\frac{\sqrt{a}}{3-\sqrt{a}}-\frac{3a+3}{a-9}`
`=\frac{3a+3}{(\sqrt{a}+3)(\sqrt{a}-3)}-\frac{2\sqrt{a}(\sqrt{a}-3)}{(\sqrt{a}+3)(\sqrt{a}-3)}-\frac{\sqrt{a}(\sqrt{a}+3)}{(\sqrt{a}+3)(\sqrt{a}-3)}`
`=\frac{3a+3-2\sqrt{a}.\sqrt{a}+6\sqrt{a}-a-3\sqrt{a}}{(\sqrt{a}+3)(\sqrt{a}-3)}`
`=\frac{3\sqrt{a}+3}{(\sqrt{a}+3)(\sqrt{a}-3)}`
`=\frac{3\sqrt{a}+3}{a-9}`
