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30 tháng 8 2017
\(P=\frac{3\sqrt{2}+\sqrt{10}}{2\sqrt{5}+\sqrt{6+2\sqrt{5}}}-\frac{3\sqrt{2}-\sqrt{10}}{2\sqrt{5}+\sqrt{6-2\sqrt{5}}}=\frac{3\sqrt{2}+\sqrt{10}}{2\sqrt{5}+\sqrt{5}+1}-\frac{3\sqrt{2}-\sqrt{10}}{2\sqrt{5}+\sqrt{5}-1}\)
\(=\frac{3\sqrt{2}+\sqrt{10}}{3\sqrt{5}+1}-\frac{3\sqrt{2}-\sqrt{10}}{3\sqrt{5}-1}=\frac{9\sqrt{10}-3\sqrt{2}+15\sqrt{2}-\sqrt{10}-9\sqrt{10}-3\sqrt{2}+15\sqrt{2}+\sqrt{10}}{44}\)
\(=\frac{24\sqrt{2}}{44}=\frac{6\sqrt{2}}{11}.\)
KH
30 tháng 8 2019
\(A=\frac{\left(\sqrt{3}+\sqrt{5}\right)\left(\sqrt{3}+\sqrt{5}\right)}{\left(\sqrt{3}-\sqrt{5}\right)\left(\sqrt{3}+\sqrt{5}\right)}+\frac{\left(\sqrt{5}-\sqrt{3}\right)\left(\sqrt{5}-\sqrt{3}\right)}{\left(\sqrt{5}+\sqrt{3}\right)\left(\sqrt{5}-\sqrt{3}\right)}\\ A=\frac{3+2\sqrt{15}+5}{3-5}+\frac{5-2\sqrt{15}+3}{5-3}\\ A=\frac{3+2\sqrt{15}+5-\left(5-2\sqrt{15}+3\right)}{-2}\\ A=\frac{4\sqrt{15}}{-2}=-2\sqrt{15}\)
KH
30 tháng 8 2019
\(B=\frac{\sqrt{5}\left(5+2\sqrt{5}\right)}{\left(\sqrt{5}\right)^2}+\frac{\sqrt{3}\left(3+\sqrt{3}\right)}{\left(\sqrt{3}\right)^2}-\left(\sqrt{5}+\sqrt{3}\right)\\ B=\frac{5\left(\sqrt{5}+2\right)}{5}+\frac{3\left(\sqrt{3}+1\right)}{3}-\left(\sqrt{5}+\sqrt{3}\right)\\ B=\sqrt{5}+2+\sqrt{3}+1-\sqrt{5}-\sqrt{3}\\ B=3\)
TB
0
16 tháng 7 2019
\(A=\frac{1}{\sqrt{3}+1}+\frac{1}{\sqrt{3}-1}\)
\(=\frac{\sqrt{3}-1}{\left(\sqrt{3}+1\right)\left(\sqrt{3}-1\right)}+\frac{\sqrt{3}+1}{\left(\sqrt{3}-1\right)\left(\sqrt{3}+1\right)}\)
\(=\frac{\sqrt{3}-1+\sqrt{3}+1}{\left(\sqrt{3}+1\right)\left(\sqrt{3}-1\right)}\)
\(=\frac{2\sqrt{3}}{\left(\sqrt{3}+1\right)\left(\sqrt{3}-1\right)}\)
\(=\frac{2\sqrt{3}}{3-1}\)
\(=\frac{2\sqrt{3}}{2}\)
\(=\sqrt{3}\)
\(B=\frac{5+\sqrt{5}}{5-\sqrt{5}}+\frac{5-\sqrt{5}}{5+\sqrt{5}}\)
\(=\frac{\sqrt{5}\left(\sqrt{5}+1\right)}{\sqrt{5}\left(\sqrt{5}-1\right)}+\frac{\sqrt{5}\left(\sqrt{5}-1\right)}{\sqrt{5}\left(\sqrt{5}+1\right)}\)
\(=\frac{\left(\sqrt{5}+1\right)}{\left(\sqrt{5}-1\right)}+\frac{\left(\sqrt{5}-1\right)}{\left(\sqrt{5}+1\right)}\)
\(=\frac{\left(\sqrt{5}+1\right)^2}{\left(\sqrt{5}-1\right)\left(\sqrt{5}+1\right)}+\frac{\left(\sqrt{5}-1\right)^2}{\left(\sqrt{5}+1\right)\left(\sqrt{5}-1\right)}\)
\(=\frac{5+2\sqrt{5}+1+5-2\sqrt{5}+1}{\left(\sqrt{5}-1\right)\left(\sqrt{5}+1\right)}\)
\(=\frac{12}{\left(\sqrt{5}-1\right)\left(\sqrt{5}+1\right)}\)
\(=\frac{12}{5-1}\)
\(=\frac{12}{4}\)
\(=3\)
\(\frac{5+\sqrt{5}}{5-\sqrt{5}}+\frac{5-\sqrt{5}}{5+\sqrt{5}}\)
\(=\frac{\left(5+\sqrt{5}\right)\left(5+\sqrt{5}\right)}{\left(5-\sqrt{5}\right)\left(5+\sqrt{5}\right)}\)\(+\frac{\left(5-\sqrt{5}\right)\left(5-\sqrt{5}\right)}{\left(5-\sqrt{5}\right)\left(5+\sqrt{5}\right)}\)
\(=\frac{\left(5+\sqrt{5}\right)^2+\left(5-\sqrt{5}\right)^2}{25-5}\)
\(=\frac{25+10\sqrt{5}+5+25-10\sqrt{5}+5}{20}\)
\(=\frac{60}{20}=30\)
Chúc bạn học tốt!