Hướng dẫn trả lời:
1) `2sqrt3 - 3sqrt12`
`= 2sqrt3 - 6sqrt3`
`= - 4sqrt3`
2) `2sqrt2 - sqrt5 + sqrt18 - sqrt20`
`= 2sqrt2 - sqrt5 + 3sqrt2 - 2sqrt5`
`= (- sqrt5 - 2sqrt5) + (2sqrt2 + 3sqrt2)`
`= - 3sqrt5+ 5sqrt2`
3) `3sqrt3 - sqrt12 + sqrt24`
`= 3sqrt3 - 2sqrt3 + 2sqrt6`
`= 2sqrt6 + sqrt3`
4) `2sqrt27 - 6sqrt48 + 4sqrt75`
`= 6sqrt3 - 24sqrt3 + 20sqrt3`
`= 2sqrt3`
5) `sqrt28 - 2sqrt14 + sqrt7 + sqrt63`
`= 2sqrt7 - 2sqrt14 + sqrt7 + 3sqrt7`
`= - 2sqrt14 + (2sqrt7 + sqrt7 + 3sqrt7)`
`= - 2sqrt14 + 6sqrt7`
6) `3sqrt5 + 4sqrt20 - 2sqrt125`
`= 3sqrt5 + 8sqrt5 - 10sqrt5`
`= sqrt5`
Đáp án:
1) `= - 4sqrt3`
2) `= - 3sqrt5+ 5sqrt2`
3) `= 2sqrt6 + sqrt3`
4) `= 2sqrt3`
5) `= - 2sqrt14 + 6sqrt7`
6) `= sqrt5`
