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`