0\Rightarrow |\sqrt5-2|=\sqrt5-2]=\\\\=\sqrt5-2-\sqrt5=2" alt="9-4\sqrt5=5+4-4\sqrt5=(\sqrt5)^2-2\cdot 2\cdot \sqrt5+2^2=(\sqrt5-2)^2\\\\\sqrt{9-4\sqrt5}-\sqrt5=\sqrt{(\sqrt5-2)^2}-\sqrt5=|\sqrt5-2|-\sqrt5=\\\\=[t.k.\; (\sqrt5-2)>0\Rightarrow |\sqrt5-2|=\sqrt5-2]=\\\\=\sqrt5-2-\sqrt5=2" align="absmiddle" class="latex-formula">