Question

[ngô đăng khôi]

help me gap pls

Answer 1

[l҉o҉n҉g҉ d҉z҉]

Bài 3

\(A=\sqrt{3-\sqrt{5}}\left(3+\sqrt{5}\right)\left(\sqrt{10}-\sqrt{2}\right)\)

\(=\sqrt{\left(3-\sqrt{5}\right)\left(3+\sqrt{5}\right)}\cdot\sqrt{3+\sqrt{5}}\cdot\sqrt{2}\left(\sqrt{5}-1\right)\)

\(=2\cdot\sqrt{6+2\sqrt{5}}\cdot\left(\sqrt{5}-1\right)=2\cdot\sqrt{\left(\sqrt{5}+1\right)^2}\cdot\left(\sqrt{5}-1\right)\)

\(=2\left(\sqrt{5}+1\right)\left(\sqrt{5}-1\right)=2\cdot4=8\left(đpcm\right)\)

\(B=\sqrt{2}\left(\sqrt{3}+1\right)\left(\sqrt{2-\sqrt{3}}\right)=\left(\sqrt{3}+1\right)\sqrt{4-2\sqrt{3}}\)

\(=\left(\sqrt{3}+1\right)\sqrt{\left(\sqrt{3}-1\right)^2}=\left(\sqrt{3}+1\right)\left(\sqrt{3}-1\right)=2\left(đpcm\right)\)

Answer 2

[l҉o҉n҉g҉ d҉z҉]

Bài 4

\(P=\frac{3\sqrt{10}+\sqrt{20}-3\sqrt{6}-\sqrt{12}}{\sqrt{5}-\sqrt{3}}=\frac{\sqrt{10}\left(\sqrt{2}+1\right)-\sqrt{6}\left(\sqrt{2}+1\right)}{\sqrt{5}-\sqrt{3}}\)

\(=\frac{\sqrt{2}\left(\sqrt{2}+1\right)\left(\sqrt{5}-\sqrt{3}\right)}{\sqrt{5}-\sqrt{3}}=2+\sqrt{2}\)

\(Q=\frac{\sqrt{2}+\sqrt{3}+\sqrt{6}+\sqrt{8}+4}{\sqrt{2}+\sqrt{3}+\sqrt{4}}=\frac{\sqrt{2}+\sqrt{3}+\sqrt{6}+2\sqrt{2}+2+2}{\sqrt{2}+\sqrt{3}+2}\)

\(=\frac{\left(\sqrt{2}+\sqrt{3}+2\right)+\sqrt{2}\left(\sqrt{2}+\sqrt{3}+2\right)}{\sqrt{2}+\sqrt{3}+2}=\frac{\left(\sqrt{2}+\sqrt{3}+2\right)\left(1+\sqrt{2}\right)}{\sqrt{2}+\sqrt{3}+2}=1+\sqrt{2}\)