Đáp án:
`1)sqrt[11-2sqrt10]`
`=sqrt[10-2sqrt10 +1]`
`=sqrt[1.10-2sqrt10 +1]`
`=sqrt[(sqrt1)^2 (sqrt10)^2 -2sqrt10 +(sqrt1)^2]`
`=sqrt[1^2 (sqrt10)^2 -2sqrt10 +1^2]`
`=sqrt[1^2 (sqrt10)^2 -2.1.1.sqrt10 +1^2]`
`=sqrt[(1.sqrt10 -1)^2]`
`=sqrt[1.sqrt10 -1]`
`=sqrt10 -1`