Đáp án+Giải thích các bước giải:
l,
`\frac{\sqrt{10}+5}{\sqrt{5}}-\sqrt{13+4\sqrt{10}}`
`=\frac{\sqrt{5}(\sqrt{2}+\sqrt{5})}{\sqrt{5}}-\sqrt{8+2.2\sqrt{2}.\sqrt{5}+5}`
`=\sqrt{2}+\sqrt{5}-\sqrt{(2\sqrt{2}+\sqrt{5})^2}`
`=\sqrt{2}+\sqrt{5}-2\sqrt{2}-\sqrt{5}`
`=-\sqrt{2}`
m,
`\frac{4}{3-\sqrt{5}}+\frac{\sqrt{10}-5}{\sqrt{5}-\sqrt{2}}`
`=\frac{4(3+\sqrt{5})}{9-5}+\frac{-\sqrt{5}(\sqrt{5}-\sqrt{2})}{\sqrt{5}-\sqrt{2}}`
`=\frac{4(\3+\sqrt{5})}{4}-\sqrt{5}`
`=3+\sqrt{5}-\sqrt{5}`
`=3`
