Olá...
[tex] \sqrt{6 + \sqrt{20} } \sqrt{6 - \sqrt{20} } \\ \sqrt{(6 + \sqrt{20)} \times (6 - \sqrt{20)} } \\ \sqrt{(6 + 2 \sqrt{5)} \times (6 - 2 \sqrt{5)} } \\ \sqrt{36 - 4 \times 5} \\ \sqrt{36 - 20} \\ \sqrt{16} \\ 4[/tex]
