Đáp án:
`sqrt{27+10sqrt2}-sqrt{18+8sqrt2}`
`= sqrt{25+2+10sqrt2}-sqrt{16+2+8sqrt2}`
`= sqrt{5^2+2xx5xxsqrt2+(sqrt2)^2}-sqrt{4^2+2xx4xxsqrt2+(sqrt2)^2}`
`= sqrt{(5+sqrt2)^2}-sqrt{(4+sqrt2)^2}`
`= |5+sqrt2|-|4+sqrt2|`
`= 5+sqrt2-(4+sqrt2)`
`= 5+sqrt2-4-sqrt2`
`= 1`