ĐKXĐ : ` x > -2`
`B = 4`
`⇔ (sqrt{x+4})/(sqrt{x+2}) = 4`
`⇔ sqrt{x+4} = 4sqrt{x+2}`
`⇔ (sqrt{x+4})^2 = (4sqrt{x+2})^2`
`⇔ x + 4 = 16(x+2)`
`⇔ x + 4 = 16x + 32`
`⇔ x - 16x = 32 - 4`
`⇔ -15x = 28`
`⇔ x = -28/15(TM)`
Vậy `S = {-28/15}`
.......................................
ĐKXĐ : `x \ge 0`
`B = 4`
`⇔ (sqrtx+4)/(sqrtx+2) = 4`
`⇔ sqrtx + 4 = 4(sqrtx+2)`
`⇔ sqrtx + 4 = 4sqrtx + 8`
`⇔ sqrtx - 4sqrtx = 8 -4`
`⇔ -3sqrtx = 4`
`⇔ sqrtx = -4/3`(vô lý)
`⇒ x ∈ ∅`
Vậy `S = \emptyset`
