Thấy : \(\sqrt[3]{x^2}=\left(x^2\right)^{\dfrac{1}{3}}=x^{\dfrac{2}{3}}\) ; \(\left(x^{\dfrac{2}{3}}\right)'=\dfrac{2}{3}x^{\dfrac{2}{3}-1}=\dfrac{2}{3}x^{-\dfrac{1}{3}}=\dfrac{2}{3}.\dfrac{1}{\sqrt[3]{x}}\)
Khi đó : \(y'=\dfrac{-2}{\sqrt[3]{x}}\) ; y' x/đ \(\Leftrightarrow x\ne0\) ; y' = 0 vô no nên h/s ko có cực trị
B.