Hướng dẫn trả lời:
1) `3 + sqrt{3}`
`= (sqrt{3})^2 + sqrt{3}`
`= sqrt{3}cdot(sqrt{3} + 1)`
2) `sqrt{2} - 2sqrt{5}`
`= sqrt{2} - sqrt{2}cdot sqrt{2}cdot sqrt{5}`
`= sqrt{2} - sqrt{2}cdot sqrt{10}`
`= sqrt{2}cdot(1 - sqrt{10})`
3) `2sqrt{7} + 7sqrt{2}`
`= sqrt{2}cdot sqrt{7}cdot sqrt{2} + sqrt{2}cdot sqrt{7}cdot sqrt{7}`
`= sqrt{14}cdot sqrt{2} + sqrt{14}cdot sqrt{7}`
`= sqrt{14}cdot(sqrt{2} + sqrt{7})`
4) `3sqrt{2} - 2sqrt{3}`
`= sqrt{2}cdot sqrt{3}cdot sqrt{3} - sqrt{2}cdot sqrt{3}cdot sqrt{2}`
`= sqrt{6}cdot sqrt{3} - sqrt{6}cdot sqrt{2}`
`= sqrt{6}cdot(sqrt{3} - sqrt{2})`
Đáp án:
1) `= sqrt{3}cdot(sqrt{3} + 1)`
2) `= sqrt{2}cdot(1 - sqrt{10})`
3) `= sqrt{14}cdot(sqrt{2} + sqrt{7})`
4) `= sqrt{6}cdot(sqrt{3} - sqrt{2})`
