Đáp án:
\(n=4\)
Giải thích các bước giải:
\(\begin{array}{l}
{3^{ - 1}}{.3^n} + {5.3^{n - 1}} = 162\\
{3^{n - 1}} + {5.3^{n - 1}} = 162\\
{3^{n - 1}}\left( {1 + 5} \right)\,\,\,\,\, = 162\\
{3^{n - 1}}.6\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 162\\
{3^{n - 1}}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 162:6\\
{3^{n - 1}}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 27\\
{3^{n - 1}}\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = {3^3}\\
n - 1\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 3\\
n\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 3 + 1\\
n\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 4
\end{array}\)
