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$L=\mathop {\lim }\limits_{ } (\sqrt[3]{n^{3 } -2n^{2}} -n)$
$L=\lim \dfrac{n^{3 } -2n^{2}-n^3}{\sqrt[3]{(n^{3 } -2n^{2})^2}+n\sqrt[3]{n^{3 } -2n^{2}} +n^2}$
$L=\lim \dfrac{-2n^{2}}{\sqrt[3]{(n^{3 } -2n^{2})^2}+n\sqrt[3]{n^{3 } -2n^{2}} +n^2}$
$L=\lim \dfrac{-2}{\dfrac{1}{n^2}.\sqrt[3]{(n^{3 } -2n^{2})^2}+\dfrac{1}{n^2}.n\sqrt[3]{n^{3 } -2n^{2}} +\dfrac{1}{n^2}.n^2}$
$L=\lim \dfrac{-2}{\sqrt[3]{\dfrac{(n^{3 } -2n^{2})^2}{n^6}}+\sqrt[3]{\dfrac{n^{3 } -2n^{2}}{n^3}} +1}$
$L= \dfrac{-2}{\sqrt[3]{1}+\sqrt[3]{1} +1}$
$L= \dfrac{-2}{3}$
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