a: \(3\sqrt{18}-2\sqrt{50}+4\sqrt{72}-\sqrt{162}\)
\(=9\sqrt{2}-10\sqrt{2}+24\sqrt{2}-9\sqrt{2}\)
\(=14\sqrt{2}\)
b: \(\dfrac{6}{\sqrt{5}-\sqrt{2}}+\dfrac{4}{\sqrt{5}-1}-3\sqrt{5}\)
\(=2\sqrt{5}+2\sqrt{2}+\sqrt{5}+1-3\sqrt{5}\)
\(=2\sqrt{2}+1\)
c: \(\sqrt{\left(\sqrt{7}-4\right)^2}\cdot\sqrt{23+4\sqrt{28}}\)
\(=\left(4-\sqrt{7}\right)\left(4+\sqrt{7}\right)\)
=9
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d: Ta có: \(\dfrac{5-\sqrt{15}}{\sqrt{5}-\sqrt{3}}-\dfrac{2\sqrt{5}-5}{\sqrt{14-2\sqrt{45}}}\)
\(=\sqrt{5}+\dfrac{\sqrt{5}\left(\sqrt{5}-2\right)}{3-\sqrt{5}}\)
\(=\sqrt{5}+\dfrac{5}{4}-\dfrac{1}{4}\sqrt{5}\)
\(=\dfrac{5}{4}+\dfrac{3}{4}\sqrt{5}\)
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