Đáp án:
`a)(3\sqrt{18}+2\sqrt{50}-4\sqrt{72}).8\sqrt{2}`
`=(3\sqrt{9.2}+2\sqrt{25.2}-4\sqrt{36.2}).8\sqrt{2}`
`=(9\sqrt{2}+10\sqrt{2}-24\sqrt{2}).8\sqrt{2}`
`=(-6\sqrt{2}).8\sqrt{2}`
`=-48.2=-96,`
`b)(-4\sqrt{20}+5\sqrt{500}-3\sqrt{45}):8\sqrt{2}`
`=(-4\sqrt{4.5}+5\sqrt{100.5}-3\sqrt{9.5}):8\sqrt{2}`
`=(-8\sqrt{5}+50\sqrt{5}-9\sqrt{5}):8\sqrt{2}`
`=33\sqrt{5}:8\sqrt{2}`
`=(33\sqrt{10})/16`