\displaystyle\frac{2}{5}=\displaystyle\lim_{n\to\infty}\frac{2n^3+3n^2}{5n^3+7n^2}=\left[\displaystyle\frac{:n^4}{:n^4}\right]=\displaystyle\lim_{n\to\infty}\frac{\frac{2}{n}+\frac{3}{n^2}}{\frac{5}{n}+\frac{7}{n^2}}=(\textrm{krivo})=\\
=\displaystyle\lim_{n\to\infty}\frac{\displaystyle\lim_{n\to\infty}\frac{2}{n}+\frac{3}{n^2}}{\displaystyle\lim_{n\to\infty}\frac{5}{n}+\frac{7}{n^2}}=\displaystyle\lim_{n\to\infty}\frac{0+\frac{3}{n^2}}{0+\frac{7}{n^2}}=\left[\displaystyle\frac{\cdot n^2}{\cdot n^2}\right]=\displaystyle\lim_{n\to\infty}\frac{3}{7}=\displaystyle\frac{3}{7}