Đề bài

Tính :

a) \(\sqrt[3]{{125}} - \sqrt[3]{8} - 2\sqrt[3]{{27}}\);

b) \(\sqrt[3]{{125}} - \sqrt[3]{{54}}.\sqrt[3]{4}\).

Lời giải chi tiết

\(\begin{array}{l}a)\;\;\sqrt[3]{{125}} - \sqrt[3]{8} - 2\sqrt[3]{{27}}\\ = \sqrt[3]{{{5^3}}} - \sqrt[3]{{{2^3}}} - 2\sqrt[3]{{{3^3}}}\\ = 5 - 2 - 2.3\\ =  - 3.\end{array}\)       

\(\begin{array}{l}b)\;\;\sqrt[3]{{125}} - \sqrt[3]{{54}}.\sqrt[3]{4}\\ = \sqrt[3]{{{5^3}}} - \sqrt[3]{{54.4}}\\ = \sqrt[3]{{{5^3}}} - \sqrt[3]{{216}}\\ = 5 - \sqrt[3]{{{6^3}}} = 5 - 6 =  - 1.\end{array}\)

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