Ta có: \(\sqrt{5}\cdot\left(\sqrt{20}+\sqrt{45}-7\sqrt{5}\right)\)
\(=\sqrt{5}\left(2\sqrt{5}+3\sqrt{5}-7\sqrt{5}\right)\)
=-10
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Ta có: \(\sqrt{5}\cdot\left(\sqrt{20}+\sqrt{45}-7\sqrt{5}\right)\)
\(=\sqrt{5}\left(2\sqrt{5}+3\sqrt{5}-7\sqrt{5}\right)\)
=-10