lim 3^n} - 1 / 2^n} - {2.3}^n} + 1 bằng

Chọn B

\[\lim \frac{{{3^n} - 1}}{{{2^n} - {{2.3}^n} + 1}} = \lim \frac{{{3^n}\left[ {1 - {{\left( {\frac{1}{3}} \right)}^n}} \right]}}{{{3^n}\left[ {{{\left( {\frac{2}{3}} \right)}^n} - 2 + {{\left( {\frac{1}{3}} \right)}^n}} \right]}} = \lim \frac{{1 - {{\left( {\frac{1}{3}} \right)}^n}}}{{{{\left( {\frac{2}{3}} \right)}^n} - 2 + {{\left( {\frac{1}{3}} \right)}^n}}} = - \frac{1}{2}\].