Đáp án + Giải thích các bước giải:
Bài `10` :
`a)` `(3+sqrt5)(3-sqrt5)-(2+sqrt3)(2-sqrt3)`
`=9-5-(4-3)`
`=9-5-4+3`
`=3`
`b)` `2sqrt3(sqrt2-3)+(2-sqrt3)^2+6sqrt3`
`=2sqrt6-6sqrt3+4-4sqrt3+3+6sqrt3`
`=2sqrt6-4sqrt3+7`
`c)` `(sqrt6+sqrt10)/(sqrt21+sqrt35)=[sqrt2(sqrt3+sqrt5)]/[sqrt7(sqrt3+sqrt5)]=(sqrt2)/(sqrt7)=sqrt14/7`
`d)`
`(sqrt405+3sqrt27)/(3sqrt3+sqrt45)`
`=(9sqrt5+9sqrt3)/(3sqrt3+3sqrt5)`
`=[9(sqrt5+sqrt3)]/[3(sqrt3+sqrt5)]=3`.
