Của em đây nhé!
`(2+sqrt3)/(sqrt2+sqrt{2+sqrt3})+(2-sqrt3)/(sqrt2-sqrt{2-sqrt3})`
`=(2sqrt2+sqrt6)/(sqrt2.sqrt2+sqrt2.sqrt{2+sqrt3})+(2sqrt2-sqrt6)/(sqrt2.sqrt2-sqrt2.sqrt{2+sqrt3})`
`=(2sqrt2+sqrt6)/(2+sqrt{4+2sqrt3})+(2sqrt2-sqrt6)/(2-sqrt{4-2sqrt3})`
`=(2sqrt2+sqrt6)/(2+sqrt{3+2sqrt3+1})+(2sqrt2-sqrt6)/(2-sqrt{3-2sqrt3+1})`
`=(2sqrt2+sqrt6)/(2+sqrt{(sqrt3+1)^2})+(2sqrt2-6)/(2-sqrt{(sqrt3-1)^2})`
`=(2sqrt2+sqrt6)/(2+sqrt3+1)+(2sqrt2-sqrt6)/(2-sqrt3+1)`
`=(2sqrt2+sqrt6)/(3+sqrt3)+(2sqrt2-sqrt6)/(3-sqrt3)`
`=((2sqrt2+sqrt6)(3-sqrt3))/(9-3)+((2sqrt2-sqrt6)(3+sqrt3))/(9-3)`
`=((2sqrt2+sqrt6)(3-sqrt3)+(2sqrt2-sqrt6)(3+sqrt3))/6`
`=(6sqrt2-2sqrt6+3sqrt6-sqrt{18}+6sqrt2+2sqrt6-3sqrt6-sqrt{18})/6`
`=(12sqrt2-2sqrt{18})/6`
`=(12sqrt2-2.sqrt{9.2})/6`
`=(12sqrt2-6sqrt2)/6`
`=(6sqrt2)/6`
`=sqrt2`.
