`a)sqrt((2-sqrt3)/(2+sqrt3))`
`=sqrt((2-sqrt3)^2/((2+sqrt3)(2-sqrt3)))`
`=sqrt((2-sqrt3)^2)/sqrt(4-3)`
`=(2-sqrt3)/sqrt1`
`=2-sqrt3`
`b)sqrt((3-sqrt5)/(3+sqrt5))`
`=sqrt((3-sqrt5)^2/((3+sqrt5)(3-sqrt5)))`
`=sqrt((3-sqrt5)^2)/sqrt(9-5)`
`=(3-sqrt5)/sqrt4`
`=(3-sqrt5)/2`