Tìm lim ( căn bậc 3 (n^3 +3n^2)-n

* Hướng dẫn giải

$$\begin{gathered} \lim \left(\sqrt[3]{n^3+3n^2}-n\right) \\ =\lim \frac{\left(\sqrt[3]{n^3+3n^2}-n\right)\left(\sqrt[3]{{\left(n^3+3n^2\right)}^2}+n\sqrt[3]{n^3+3n^2}+n^2\right)}{\sqrt[3]{{\left(n^3+3n^2\right)}^2}+n\sqrt[3]{n^3+3n^2}+n^2} \\ =\lim \frac{3n^2}{\sqrt[3]{{\left(n^3+3n^2\right)}^2}+n\sqrt[3]{n^3+3n^2}+n^2} \\ =\lim \frac{3}{\sqrt[3]{{\left(1+\frac{3}{n}\right)}^2}+\sqrt[3]{1+\frac{3}{n}}+1}=1 \end{gathered}$$

Chọn đáp án A