Question

(1) rút gọn biểu thức:

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

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

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

d) D= \(\sqrt[3]{27}-\sqrt[3]{-8}-\sqrt[3]{125}\)

giúp mk vs ạ mai mk hc rồi

Answer 1

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

b) \(\Leftrightarrow B=\sqrt{7-2\sqrt{12}}+\sqrt{12+2\sqrt{27}}=\sqrt{\left(2-\sqrt{3}\right)^2}+\sqrt{\left(3+\sqrt{3}\right)^2}=2-\sqrt{3}+3+\sqrt{3}=5\)

c) \(\Leftrightarrow C=\dfrac{3-\sqrt{5}+3+\sqrt{5}}{\left(3+\sqrt{5}\right)\left(3-\sqrt{5}\right)}=\dfrac{6}{4}=\dfrac{3}{2}\)

d) \(\Leftrightarrow D=3-\left(-2\right)-5=0\)