Đáp án:
`(4+\sqrt{15})(\sqrt{10}-sqrt6).\sqrt{4-\sqrt{15}`
`=\sqrt{4+\sqrt{15}}^2.\sqrt{4-\sqrt{15}}(\sqrt{10}-sqrt6)`
`=\sqrt{(4+\sqrt{15})(4-\sqrt{15})}.(\sqrt{10}-sqrt6).\sqrt{4+\sqrt{15}}`
`=\sqrt{16-15}.\sqrt2(\sqrt5-sqrt3).\sqrt{4+\sqrt{15}`
`=1.(\sqrt5-sqrt3).\sqrt{8+2\sqrt{15}`
`=(sqrt5-sqrt3)sqrt{5+2sqrt{3.5}+3}`
`=(sqrt5-sqrt3)sqrt{(sqrt5+sqrt3)^2}`
`=(sqrt5-sqrt3)(sqrt5+sqrt3)`
`=5-3=2(Đpcm)`.