a: \(=\dfrac{2}{5}\cdot2\sqrt{5}-\left|2-\sqrt{5}\right|\)
\(=\dfrac{4}{5}\sqrt{5}-\sqrt{5}+2=-\dfrac{1}{5}\sqrt{5}+2\)
b: \(=\dfrac{4\left(3+\sqrt{7}\right)}{9-7}-\dfrac{3\left(\sqrt{7}+2\right)}{7-4}\)
\(=2\left(3+\sqrt{7}\right)-\sqrt{7}-2\)
\(=6+2\sqrt{7}-\sqrt{7}-2=\sqrt{7}+4\)
c: \(=3\cdot2\sqrt{13}-2\cdot\left(\sqrt{13}-3\right)-\dfrac{3\left(4-\sqrt{13}\right)}{16-13}\)
\(=6\sqrt{13}-2\sqrt{13}+6-4+\sqrt{13}\)
\(=5\sqrt{13}+2\)
a) \(A=\dfrac{2}{5}\cdot\sqrt{20}-\sqrt{\left(2-\sqrt{5}\right)^2}\)
\(A=\dfrac{2}{5}\cdot2\sqrt{5}-\left|2-\sqrt{5}\right|\)
\(A=\dfrac{4}{5}\sqrt{5}+2-\sqrt{5}\)
\(A=-\dfrac{1}{5}\sqrt{5}+2\)
b) \(B=\dfrac{4}{3-\sqrt{7}}-\dfrac{3}{\sqrt{7}-2}\)
\(B=\dfrac{4\left(3+\sqrt{7}\right)}{\left(3-\sqrt{7}\right)\left(3+\sqrt{7}\right)}-\dfrac{3\left(\sqrt{7}+2\right)}{\left(\sqrt{7}-2\right)\left(\sqrt{7}+2\right)}\)
\(B=\dfrac{4\left(3+\sqrt{7}\right)}{9-7}-\dfrac{3\left(\sqrt{7}+2\right)}{7-4}\)
\(B=2\left(3+\sqrt{7}\right)-\left(\sqrt{7}+2\right)\)
\(B=6+2\sqrt{7}-\sqrt{7}-2\)
\(B=\sqrt{7}+4\)
c) \(C=3\sqrt{52}-2\sqrt{\left(3-\sqrt{13}\right)^2}-\dfrac{3}{4+\sqrt{13}}\)
\(C=3\cdot2\sqrt{13}-2\left|3-\sqrt{13}\right|-\dfrac{3\left(4-\sqrt{13}\right)}{\left(4-\sqrt{13}\right)\left(4+\sqrt{13}\right)}\)
\(C=6\sqrt{13}+2\left(3-\sqrt{13}\right)-\dfrac{3\left(4-\sqrt{13}\right)}{16-13}\)
\(C=6\sqrt{13}+6-2\sqrt{13}-4+\sqrt{13}\)
\(C=5\sqrt{13}+2\)
giúp e vs ạ ;-;
giúp e vs ạ :<