\(\sqrt{7-4\sqrt{3}}=\sqrt{2^2-2.2\sqrt{3}+3}=\sqrt{\left(2-\sqrt{3}\right)^2}=2-\sqrt{3}\)
\(\sqrt{8+10\sqrt{7-4\sqrt{3}}}=\sqrt{8+10\left(2-\sqrt{3}\right)}=\sqrt{28-10\sqrt{3}}=\sqrt{5^2-2.5.\sqrt{3}+3}\)
\(=\sqrt{\left(5-\sqrt{3}\right)^2}=5-\sqrt{3}\)
Vậy:
\(\sqrt{9-\sqrt{5\sqrt{3}+5\sqrt{8+10\sqrt{7-4\sqrt{3}}}}}=\sqrt{9-\sqrt{5\sqrt{3}+5\left(5-\sqrt{3}\right)}}\)
\(=\sqrt{9-\sqrt{25}}=\sqrt{9-5}=2\)