2 câu trả lời
Lời giải:
\(\begin{array}{l}\sqrt{9-4\sqrt{5}}-\sqrt{5}\\=\sqrt{5-2.2.\sqrt{5}+4}-\sqrt{5}\\=\sqrt{(\sqrt{5}-2)^2}-\sqrt{5}\\=|\sqrt{5}-2|-\sqrt{5}\\=\sqrt{5}-2-\sqrt{5}=-2\end{array}\)
Lời giải:
\(\begin{array}{l}\sqrt{9-4\sqrt{5}}-\sqrt{5}\\=\sqrt{5-2.2.\sqrt{5}+4}-\sqrt{5}\\=\sqrt{(\sqrt{5}-2)^2}-\sqrt{5}\\=|\sqrt{5}-2|-\sqrt{5}\\=\sqrt{5}-2-\sqrt{5}=-2\end{array}\)