`a) (sqrt{5}+1)^2`
`=5+2sqrt{5}+1`
`=6+2sqrt{5} (\text{đpcm})`
`b) \sqrt{6+2sqrt{5}}-sqrt{5}`
`=sqrt{5+2sqrt{5}+1}-sqrt{5}`
`=sqrt{(sqrt{5}+1)^2}-sqrt{5}`
`=|sqrt{5}+1|-sqrt{5}`
`=sqrt{5}+1-sqrt{5}`
`=1 (\text{đpcm})`
`c) sqrt{3+2sqrt{2}}+sqrt{3-2sqrt{2}}`
`=sqrt{2+2sqrt{2}+1}+sqrt{2-2sqrt{2}+1}`
`=sqrt{(sqrt{2}+1)^2}+sqrt{(sqrt{2}-1)^2}`
`=|sqrt{2}+1|+|sqrt{2}-1|`
`=sqrt{2}+1+sqrt{2}-1`
`=2sqrt{2} (\text{đpcm})`
