giúp em với cảm ơn mn🫰

Đáp án: + Giải thích các bước giải:

`7. sqrt(x-1)  -2/9 sqrt(9x-9) + 6sqrt(4x+4) =0` `(x>=1)`

`⇔ sqrt(x-1) - 2/9 . 3 . sqrt(x-1) + 6.2.sqrt(x+1)=0`

`⇔ sqrt(x-1) - 2/3 sqrt(x-1) + 12sqrt(x+1)=0`

`⇔ 1/3 sqrt(x-1) + 12sqrt(x+1)=0`

Ta có : ` 1/3 sqrt(x-1) + 12sqrt(x+1) > 0 ∀x ≥1`

`⇒` `x` `∈` `∅`

   Vậy `x` `∈` `∅`

`8. sqrt(9x+18) - 1/4 sqrt(16x+32) = 2-sqrt(x+2)` `(x>=-2)`

`⇔ 3sqrt(x+2) - 1/4 . 4sqrt(x+2) + sqrt(x+2)=2`

`⇔ 3sqrt(x+2)-sqrt(x+2)+sqrt(x+2)=2`

`⇔ sqrt(x+2)=2/3`

`⇔ x+2=4/9`

`⇔ x = -{14}/9` (TMĐK)

   Vậy `x=-{14}/9`

`9. sqrt(x^2-8x+16)=3`

`⇔ sqrt((x-4)^2) = 3`

`⇔ |x-4| = 3`

`⇒` `x` `∈` `{1,7}`

  Vậy `x` `∈` `{1,7}`