Cho hàm số [f left( x right) = sqrt[3]{x} ]. Giá trị của f′(8) bằng: [f left( x right) = sqrt[3]{x} = {x^{ frac{1}{3}}} Rightarrow f' left( x right) = frac{1}{3}.{x^{ frac{1}{3} -...

\[f\left( x \right) = \sqrt[3]{x} = {x^{\frac{1}{3}}} \Rightarrow f'\left( x \right) = \frac{1}{3}.{x^{\frac{1}{3} - 1}} = \frac{1}{3}{x^{ - \frac{2}{3}}} = \frac{1}{3}\frac{1}{{{x^{\frac{2}{3}}}}} = \frac{1}{3}\frac{1}{{\sqrt[3]{{{x^2}}}}}\]

\[ \Rightarrow f'\left( 8 \right) = \frac{1}{3}.\frac{1}{{\sqrt[3]{{{8^2}}}}} = \frac{1}{{12}}\]