Question

[Trang Nguyễn]

1) rút gọn 

A= \(3\sqrt{2}+5\sqrt{8}-2\sqrt{50}\)

B= \(\dfrac{1}{3+\sqrt{5}}+\dfrac{1}{3-\sqrt{5}}\)

C= \(\sqrt{7-4\sqrt{3}}+\sqrt{12+6\sqrt{3}}\)

Giúp mk vs ạ mk cần gấp 

Answer 1

[Hồng Phúc]

\(A=3\sqrt{2}+5\sqrt{8}-2\sqrt{50}\)

\(=3\sqrt{2}+10\sqrt{2}-10\sqrt{2}\)

\(=3\sqrt{2}\)

Answer 2

[Hồng Phúc]

\(B=\dfrac{1}{3+\sqrt{5}}+\dfrac{1}{3-\sqrt{5}}\)

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

\(=\dfrac{3-\sqrt{5}+3+\sqrt{5}}{9-5}\)

\(=\dfrac{3}{2}\)