~Tham khảo :
ĐK : `a > 0 , a > 0 , a \ne b`
`((a+b-2sqrt{ab})/(sqrta-sqrtb)) \div (1/(sqrta+sqrtb))`
`= (a-2sqrt{ab}+b)/(sqrta-sqrtb) * (sqrta+sqrtb)`
`= (sqrta^2-2sqrtasqrtb+sqrtb^2)/(sqrta-sqrtb) * (sqrta+sqrtb)`
`= ((sqrta-sqrtb)^2)/(sqrta-sqrtb) * (sqrta+sqrtb)`
`= (sqrta-sqrtb)(sqrta+sqrtb)`
`= sqrta^2 - sqrtb^2`
`= a - b`
`->`đpcm