a) \(\lim \left( {{n^2} + 2n - 5} \right) = \lim {n^2}\left( {1 + \frac{2}{n} - \frac{5}{{{n^2}}}} \right) = + \infty \)
b) \(\lim \left( { - {n^3} - 3{n^2} - 2} \right) = \lim \left[ { - {n^3}\left( {1 + \frac{3}{n} + \frac{2}{{{n^3}}}} \right)} \right] = - \infty \)
c)
\(\lim [{4^n} + {( - 2)^n}] = \lim {4^n}[1 + {( - \frac{1}{2})^n}] = + \infty \)-- Mod Toán 11