Question

Mấy câu này làm sao vậy mn

 

Answer 1

Câu 21: D

Câu 15: \(=\sqrt{3}-1+\sqrt{3}+1=2\sqrt{3}\)

Câu 11: \(=\dfrac{\sqrt{3}\left(\sqrt{3}+1\right)}{6}=\dfrac{3+\sqrt{3}}{6}\)

Answer 2

5. \(\sqrt{\left(1-\sqrt{2}\right)^2}-\sqrt{\left(1+\sqrt{2}\right)^2}=\left|1-\sqrt{2}\right|-\left|1+\sqrt{2}\right|=\sqrt{2}-1-1-\sqrt{2}=-2\)

6. \(\dfrac{1}{\sqrt{5}+2}=\dfrac{\sqrt{5}-2}{\left(\sqrt{5}-2\right)\left(\sqrt{5}+2\right)}=\dfrac{\sqrt{5}-2}{5-4}=\sqrt{5}-2\)

Answer 3

\(\sqrt{\left(1-\sqrt{2}\right)^2}\sqrt{\left(1+\sqrt{2}\right)^2}\)

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

\(=\sqrt{\left(1-2\right)^2}=\sqrt{\left(-1\right)^2}=1\)