Question

B=\(4\sqrt{20}\)+\(\sqrt{6-2\sqrt{5}}\) -\(15\sqrt{\frac{1}{5}}\)

đang cần gấp ạ

Answer 1

Lời giải:
\(B=4\sqrt{20}+\sqrt{6-2\sqrt{5}}-15\sqrt{\frac{1}{5}}\)

\(=4\sqrt{4}.\sqrt{5}+\sqrt{5-2\sqrt{5}+1}-3.\sqrt{25}.\sqrt{\frac{1}{5}}\)

\(=8\sqrt{5}+\sqrt{(\sqrt{5}-1)^2}-3\sqrt{5}\)

\(=(8-3)\sqrt{5}+(\sqrt{5}-1)=5\sqrt{5}+\sqrt{5}-1=6\sqrt{5}-1\)

Answer 2

B = \(4\sqrt{20}+\sqrt{6-2\sqrt{5}}-15\sqrt{\frac{1}{5}}\)

= \(4\sqrt{4\times5}+\sqrt{5-2\sqrt{5}+1}-\sqrt{15}^2\times\sqrt{\frac{1}{5}}\)

= \(8\sqrt{5}+\sqrt{\left(\sqrt{5}-1\right)^2}-3\sqrt{5}\)

= \(5\sqrt{5}+\sqrt{5}-1=6\sqrt{5}-1\)