~ Gửi bạn nhea ~
Ta có :
`(1-(x+sqrtx)/(sqrtx+1))(1/(1-sqrtx)+2/(sqrtx-3))`
`= (1-(sqrtx(sqrtx+1))/(sqrtx+1))(sqrtx-3+2(1-sqrtx))/((1-sqrtx)(sqrtx-3))`
`= (1-sqrtx) * (sqrtx-3+2-2sqrtx)/((1-sqrtx)(sqrtx-3))`
`= (-sqrtx-1)/(sqrtx-3)`
ĐKXĐ : `x \ne 9 , x \ge 0 , x \ne 1`
`\to (-sqrtx-1)/(sqrtx-3) = -2`
`\to -sqrtx - 1 = -2(sqrtx-3)`
`\to -sqrtx - 1 = -2sqrtx + 6`
`\to -sqrtx + 2sqrtx = 6 + 1`
`\to sqrtx = 7`
`\to x =49` (TM)
Vậy `S = {49}`
