ĐKXĐ : `a \ge 0 , sqrta + 1 \ne 0 , a + sqrta \ne 0 , a + 2sqrta + 1 \ne 0`
`sqrta + 1 \ne 0`
`⇔ sqrta \ne -1`
`⇔ x ∈ ∅`
`a + sqrta \ne 0`
`⇔ a = a^2`
`⇔ a \ne 0`
`a+2sqrta+1\ne0`
`⇔ x ∈ ∅`
`⇒`ĐKXĐ : `a \ne 0 , a \ge 0 ⇒ a> 0`
`Q = (1/(sqrta+1) * 1/(a+sqrta)) : (sqrta-1)/(a+2sqrta+1)`
`= 1/((sqrta+1)sqrta(sqrta+1)) * (sqrta^2+2*sqrta*1+1^2)/(sqrta-1)`
`= 1/((sqrta+1)sqrta(sqrta+1)) * ((sqrta+1)^2)/(sqrta-1)`
(Ta có thêm ĐKXĐ: `sqrta - 1 \ne 0 ⇒ sqrta \ne 1 ⇒ x \ne 1`)
`= 1/(sqrta(sqrta+1)) * (sqrta+1)/(sqrta-1)`
`= 1/sqrta * 1/(sqrta-1)`
`= 1/(sqrta(sqrta-1))`
`= 1/(a-sqrta)`
