Question

cứu em câu b,c với ạ

Answer 1

b: \(B=\sqrt{\left(2\sqrt{5}-5\right)^2}+\sqrt{29-12\sqrt{5}}\)

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

\(=\left|5-2\sqrt{5}\right|+\left|2\sqrt{5}-3\right|\)

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

c: \(C=\dfrac{6}{\sqrt{7}-1}-14\sqrt{\dfrac{1}{7}}+\dfrac{\sqrt{21}+2\sqrt{7}}{2+\sqrt{3}}\)

\(=\dfrac{6\left(\sqrt{7}+1\right)}{7-1}-2\sqrt{7}+\dfrac{\sqrt{7}\left(2+\sqrt{3}\right)}{2+\sqrt{3}}\)

\(=\sqrt{7}+1-2\sqrt{7}+\sqrt{7}=1\)