căn(9x-18) + 2căn(25x-50) = 26

$\sqrt{9x-18}$ + `2`$\sqrt{25x-50}$ `= 26`  ĐK : `x ≥ 2` 
`<=>` $\sqrt{9.(x-2)}$ + 2$\sqrt{25.(x-2)}$ `= 26` 
`<=> 3`$\sqrt{x-2}$ `+ 10`$\sqrt{x-2}$ `= 26` 
`<=>` `13`$\sqrt{x-2}$ `= 26` 
`<=>` $\sqrt{x-2}$ `= 2` 
`<=> x - 2 = 4` 
`<=> x = 6` ( Tm ) 
Vậy `S = {6}`