Không dùng MTCT, tính giá trị của các biểu thức sau:
a) \(\left( {\sqrt[3]{{64}} - \sqrt[3]{{27}}} \right).\sqrt[3]{{\frac{{125}}{8}}}\);
b) \(\frac{{5\sqrt[3]{{ - 8}} - 10\sqrt[3]{{0,008}} + 3\sqrt[3]{{343}}}}{{\sqrt[3]{{0,064}} + \sqrt[3]{{0,125}}}}\).
\({\left( {\sqrt[3]{a}} \right)^3} = \sqrt[3]{{{a^3}}} = a\)
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a) \(\left( {\sqrt[3]{{64}} - \sqrt[3]{{27}}} \right).\sqrt[3]{{\frac{{125}}{8}}} \)
\(= \left( {\sqrt[3]{{{4^3}}} - \sqrt[3]{{{3^3}}}} \right).\sqrt[3]{{{{\left( {\frac{5}{2}} \right)}^3}}} \)
\(= \left( {4 - 3} \right).\frac{5}{2} = \frac{5}{2}\);
b) \(\frac{{5\sqrt[3]{{ - 8}} - 10\sqrt[3]{{0,008}} + 3\sqrt[3]{{343}}}}{{\sqrt[3]{{0,064}} + \sqrt[3]{{0,125}}}} \)
\(= \frac{{5\sqrt[3]{{{{\left( { - 2} \right)}^3}}} - 10\sqrt[3]{{{{0,2}^3}}} + 3\sqrt[3]{{{7^3}}}}}{{\sqrt[3]{{{{0,4}^3}}} + \sqrt[3]{{{{0,5}^3}}}}} \\= \frac{{5.\left( { - 2} \right) - 10.0,2 + 3.7}}{{0,4 + 0,5}} \\= \frac{9}{{0,9}} = 10\).