lim (n^2 + 2n)/(n + 1) bằng

Ta có $\lim \frac{{\mathrm{n}}^2+2\mathrm{n}}{\mathrm{n}+1}=\lim \frac{1+\frac{2}{\mathrm{n}}}{\frac{1}{\mathrm{n}}+\frac{1}{{\mathrm{n}}^2}}.$ 

$\left.\begin{array}{l}\lim \left(1+\frac{2}{\mathrm{n}}\right)=1>0\\ \lim \left(\frac{1}{\mathrm{n}}+\frac{1}{{\mathrm{n}}^2}\right)=0\\ \frac{1}{\mathrm{n}}+\frac{1}{{\mathrm{n}}^2}>0,\forall \mathrm{n}\end{array}\right\}\Rightarrow \lim \frac{1+\frac{2}{\mathrm{n}}}{\frac{1}{\mathrm{n}}+\frac{1}{{\mathrm{n}}^2}}=+\infty .$

Vậy chọn phương án B.