Đáp án+Giải thích các bước giải:
`C=(\sqrt5+\sqrt3)(5-\sqrt15)`
`=\sqrt5(5-\sqrt15)+\sqrt3(5-\sqrt15)`
`=5\sqrt5-\sqrt75+5\sqrt3-\sqrt45`
`=5\sqrt5-\sqrt{25.3}+5\sqrt3-\sqrt{9.5}`
`=5\sqrt5-5\sqrt3+5\sqrt3-3\sqrt5`
`=5\sqrt5-3\sqrt5`
`=2\sqrt5`
Vậy `C=2\sqrt5`
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`D=(\sqrt32-\sqrt50+\sqrt27)(\sqrt27+\sqrt50-\sqrt32)`
`=[\sqrt27+(\sqrt32-\sqrt50)].[\sqrt27-(\sqrt32-\sqrt50)]`
`=(\sqrt27)^2-(\sqrt32-\sqrt50)^2`
`=27-(\sqrt{16.2}-\sqrt{25.2})^2`
`=27-(4\sqrt2-5\sqrt2)^2`
`=27-(-\sqrt2)^2`
`=27-2`
`=25`
Vậy `D=25`