Giải thích các bước giải:
`a, \ 4+2sqrt3`
`=3+2sqrt3+1`
`=(sqrt3+1)^2`
`b, \ 7-4sqrt3`
`=4-2.2.sqrt3+3`
`=(2-sqrt3)^2`
`c, \ 12-4sqrt5`
`=10-2.sqrt10 . sqrt2+2`
`=(sqrt10-sqrt2)^2`
`d, \ 17-12sqrt2`
`=9-2.3.2sqrt2+8`
`=(3-sqrt8)^2`
`e, \ (2-sqrt3)/2=(4-2sqrt3)/4`
`=(3-2sqrt3+1)/4=((sqrt3-1)^2)/(2^2)`
`=((sqrt3-1)/2)^2`