a) Ta có: \(\sqrt{\dfrac{-2t}{3}}\cdot\sqrt{\dfrac{-3t}{8}}\)
\(=\sqrt{\dfrac{6t^2}{24}}\)
\(=\sqrt{\dfrac{t^2}{4}}=\dfrac{\left|t\right|}{2}=-\dfrac{t}{2}\)
b) Ta có: \(\sqrt{\dfrac{2a^3}{b}}:\sqrt{\dfrac{ab^3}{8}}\)
\(=\sqrt{\dfrac{2a^3}{b}\cdot\dfrac{8}{ab^3}}\)
\(=\sqrt{\dfrac{16a^3}{ab^4}}\)
\(=\sqrt{\dfrac{16a^2}{b^4}}=\dfrac{\left|4a\right|}{b^2}=-\dfrac{4a}{b^2}\)
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