$\Large \mathrm{lim}(2n^4+5n^2-7n)$ bằng $\Large -\infty$. 0. 2. $\Lar

$\Large \mathrm{lim}(2n^4+5n^2-7n)$ bằng

• A.

  $\Large -\infty$.

• B.

  0.

• C.

  2.

• D.

  $\Large +\infty$.

Ta có: 

$\Large 2n^4+5n^2-7n=n^4\left(2+\dfrac{5}{n^2}-\dfrac{7}{n^3}\right)$

Vì $\Large \mathrm{lim}n^4=+\infty$ và $\Large \mathrm{lim}\left(2+\dfrac{5}{n^2}-\dfrac{7}{n^3}\right)=2$

nên $\Large \mathrm{lim}(2n^4+5n^2-7n)=+\infty$

Chọn đáp án D.