Tìm x $\sqrt{9x+9}$ + $\sqrt{4x+4}$ + $\sqrt{x+1}$ = 18

Đáp án:

 `x=8`

Giải thích các bước giải:

`sqrt(9x+9)+sqrt(4x+4)+sqrt(x+1)=18“ (x ge -1)`

`<=>sqrt(9(x+1))+sqrt(4(x+1))+sqrt(x+1)=18`

`<=>3sqrt(x+1)+2sqrt(x+1)+sqrt(x+1)=18`

`<=>(3+2+1).sqrt(x+1)=18`

`<=>6sqrt(x+1)=18`

`<=>sqrt(x+1)=3`

`<=>(sqrt(x+1))^2=3^2`

`<=>x+1=9`

`<=>x=8(tm)`

`Vậy` `x=8`