Question

Answer 1

=20,39819798

Answer 2

`sqrt{9-4sqrt5}+3sqrt5+11`

`=sqrt{5-2.2.sqrt5+4}+3sqrt5+11`

`=sqrt{(sqrt5-2)^2}+3sqrt5+11`

`=sqrt5-2+3sqrt5+11`

`=9+4sqrt5`

Answer 3

\(\sqrt{9-4\sqrt 5}+3\sqrt 5+11\\=\sqrt{4-4\sqrt 5+5}+3\sqrt 5+11\\=\sqrt{(2-\sqrt 5)^2}+3\sqrt 5+11\\=|2-\sqrt 5|+3\sqrt 5+11\\=\sqrt 5-2+3\sqrt 5+11\\=4\sqrt 5+9\)

Answer 4

Sửa đề: \(\sqrt{9-4\sqrt{5}}+3\sqrt{5}+11\)

Ta có: \(\sqrt{9-4\sqrt{5}}+3\sqrt{5}+11\)

\(=\sqrt{5-2\cdot\sqrt{5}\cdot2+4}+3\sqrt{5}+11\)

\(=\sqrt{\left(\sqrt{5}-2\right)^2}+3\sqrt{5}+11\)

\(=\sqrt{5}-2+3\sqrt{5}+11\)

\(=9+4\sqrt{5}\)