Question

2 raiz de 20 menos 4 raiz de 5?

Answer 1

$\ \ \ 2\sqrt{20}-4\sqrt{5}\\ \\=2\sqrt{4\cdot 5}-4\sqrt{5}\\ \\=2\sqrt{4}\cdot \sqrt{5}-4\sqrt{5}\\ \\=2\cdot 2\cdot \sqrt{5}-4\sqrt{5}\\ \\=4\sqrt{5}-4\sqrt{5}\\ \\=0$