`7)2\sqrt{4x-12}-1/3\sqrt{9x-27}-9=0 `

`2\sqrt{4(x-3)}-1/3\sqrt{9(x-3)}=9 `

`2.2\sqrt{x-3}-1/3  .3\sqrt{x-3}=9 `

`4\sqrt{x-3}-\sqrt{x-3}=9 `

`(4-1)\sqrt{x-3}=9 `

`3\sqrt{x-3}=9 `

`\sqrt{x-3}=3(x>=3) `

`x-3=3^2` 

`x-3=9 `

`x=12(TMĐK) `

Vậy=..

`9)3\sqrt{x^2+2}-1/2\sqrt{4x^2+8}=4 `

`3\sqrt{x^2+2}-1/2\sqrt{4(x^2+2)}=4 `

`3\sqrt{x^2+2}-1/2  .2\sqrt{x^2+2}=4 `

`3\sqrt{x^2+2}-\sqrt{x^2+2}=4 `

(3-1)\sqrt{x^2+2}=4 `

`2\sqrt{x^2+2}=4 `

`\sqrt{x^2+2}=2 `

`x^2+2=2^2 `

`x^2+2=4 `

`x^2=2 `

`x^2=+-\sqrt{2} `

`x=+-\sqrt{2} `

Vậy..

`11)\sqrt{16x+16}-\sqrt{9x+9}+2\sqrt{4x+4}=10 `

`\sqrt{16(x+1)}-\sqrt{9(x+1)}+2\sqrt{4(x+1)}=10 `

`4\sqrt{x+1}-3\sqrt{x+1}+2.2\sqrt{x+1}=10 `

`4\sqrt{x+1}-3\sqrt{x+1}+4\sqrt{x+1}=10 `

`(4-3+4)\sqrt{x+1}=10 `

`5\sqrt{x+1}=10 `

`\sqrt{x+1}=2(x>=-1) `

`x+1=2^2 `

`x+1=4 `

`x=3(TMĐK) `

Vậy..