Question

[Như Ý]

bài 68

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

b) \(\dfrac{\sqrt[3]{135}}{\sqrt[3]{5}}-\sqrt[3]{54}.\sqrt[3]{4}\)

bài 69 : so sánh

a) 3 và \(\sqrt[3]{123}\)

b)

Answer 1

[Trần Dương]

Bài 68 :

a ) \(\sqrt[3]{27}-\sqrt[3]{8}-\sqrt[3]{125}=3-2-5=-4\)

b ) \(\dfrac{\sqrt[3]{135}}{\sqrt[3]{5}}-\sqrt[3]{54}.\sqrt[3]{4}=\sqrt[3]{\dfrac{135}{5}}-\sqrt[3]{54.4}=\sqrt[3]{27}-\sqrt[3]{216}=3-6=-3\)

Answer 2

[Trần Dương]

Bài 69 :

a ) Ta có : \(\left\{{}\begin{matrix}3^3=27\\\left(\sqrt[3]{123}\right)^3=123\end{matrix}\right.\)

Vì 27 < 123 nên suy ra \(3< \sqrt[3]{123}\)

Vậy \(3< \sqrt[3]{123}\)