Question

[Nguyễn Quỳnh Chi]

Tính

1) \(\sqrt{18}.\sqrt{2}\)

2) \(\sqrt{15^2-9^2}\)

3) \(\sqrt{46-6\sqrt{5}}-\sqrt{46+6\sqrt{5}}\)

4)\(\sqrt{21+6\sqrt{6}}-\sqrt{21-6\sqrt{6}}\)

5) \(\left(2+\sqrt{5}\right).\sqrt{9-4\sqrt{5}}\)

6)\(\left(3-\sqrt{2}\right).\sqrt{7+4\sqrt{3}}\)

7)\(\left(\sqrt{3}+\sqrt{5}\right).\sqrt{7-2\sqrt{10}}\)

8)\(\left(\sqrt{6}+\sqrt{10}\right).\sqrt{4-\sqrt{15}}\)

9) \(\sqrt{2}.\left(\sqrt{8}-\sqrt{32}+3\sqrt{18}\right)\)

10) \(\sqrt{2}\left(\sqrt{2}-\sqrt{3-\sqrt{5}}\right)\)

11) \(\sqrt{3}-\sqrt{2}-\sqrt{\left(\sqrt{3}+\sqrt{2}\right)^2}\)

12) \(\left(\sqrt{2}-\sqrt{3+\sqrt{5}}\right).\sqrt{2}+2\sqrt{5}\)

Answer 1

[Nguyễn Lê Phước Thịnh]

1: \(=\sqrt{36}=6\)

2: \(=\sqrt{\left(15-9\right)\left(15+9\right)}=\sqrt{24\cdot6}=12\)

3: \(=3\sqrt{5}-1-3\sqrt{5}-1=-2\)

4: \(=3\sqrt{2}+\sqrt{3}-3\sqrt{2}+\sqrt{3}=2\sqrt{3}\)

5: \(=\left(2+\sqrt{5}\right)\left(\sqrt{5}-2\right)=5-4=1\)