6: \(=3\cdot2\sqrt{3}-4\cdot3\sqrt{3}+5\cdot4\sqrt{3}=14\sqrt{3}\)

7: \(=2\sqrt{3}+5\sqrt{3}-4\sqrt{3}=3\sqrt{3}\)

8: \(=2\cdot4\sqrt{2}+4\cdot2\sqrt{2}-5\cdot3\sqrt{2}=\sqrt{2}\)

9: \(=3\cdot2\sqrt{5}-2\cdot3\sqrt{5}+4\sqrt{5}=4\sqrt{5}\)

10: \(=2\cdot2\sqrt{6}-2\cdot3\sqrt{6}+3\sqrt{6}-5\sqrt{6}=-4\sqrt{6}\)

Đúng ko các bạn 

Căn 2 + Căn 8 + Căn 50 mới bằng 8 căn 2

\(\sqrt[]{2}+\sqrt[]{8}+\sqrt[]{52}\)

\(=\sqrt[]{2}+2\sqrt[]{2}+2\sqrt[]{13}\)

\(=3\sqrt[]{2}+2\sqrt[]{13}\)

\(\Rightarrow\sqrt[]{2}+\sqrt[]{8}+\sqrt[]{52}\ne8\sqrt[]{2}\)

Câu này đề hỏi gì vậy em?

\(3\sqrt{2}-4\sqrt{8}+\sqrt{32}-\sqrt{50}\)

= \(3\sqrt{2}-8\sqrt{2}+4\sqrt{2}-5\sqrt{2}\)

= \(-6\sqrt{2}\)

các ý còn lại làm tương tự

\(\sqrt{5}-17\sqrt{3}\)

\(4\sqrt{12}-3\sqrt{45}-5\sqrt{75}+2\sqrt{125}\\ =8\sqrt{3}-9\sqrt{5}-25\sqrt{3}+10\sqrt{5}\\ \sqrt{5}-17\sqrt{3}\)

=\(\frac{1}{\sqrt{5}}+\frac{5\left(2\sqrt{5}+5\sqrt{5}\right)}{\left(2\sqrt{5}+5\sqrt{5}\right)\left(2\sqrt{5}-5\sqrt{5}\right)}+\frac{2\left(2+\sqrt{5}\right)}{\left(2-\sqrt{5}\right)\left(2+\sqrt{5}\right)}\)

=\(\frac{1}{\sqrt{5}}-7\sqrt{5}-2\sqrt{5}-4\)=\(\frac{1-45-4\sqrt{5}}{\sqrt{5}}=\frac{-44\sqrt{5}-20}{5}\)

a: \(=9\sqrt{2}-4\sqrt{2}+4\sqrt{2}+9\sqrt{2}=18\sqrt{2}\)

b: \(=8\sqrt{3}-12\sqrt{3}+5\sqrt{3}+2\sqrt{3}=3\sqrt{3}\)

c: \(=2\sqrt{21}\)