Nội dung bài giảng
Bài 68. Tính
a)\(\root 3 \of {27} - \root 3 \of { - 8} - \root 3 \of {125} \)
b) \({{\root 3 \of {135} } \over {\root 3 \of 5 }} - \root 3 \of {54} .\root 3 \of 4 \)
Hướng dẫn giải:
a)
\(\sqrt[3]{27}-\sqrt[3]{-8}-\sqrt[3]{125}=3+2-5=0\)
b)
\(\frac{\sqrt[3]{135}}{\sqrt[3]{5}}-\sqrt[3]{54}.\sqrt[3]{4}\)
\(=\sqrt[3]{\frac{135}{5}}-\sqrt[3]{54.4}\)
\(=\sqrt[3]{27}-\sqrt[3]{216}\)
\(=3-6=-3\)