Giải thích các bước giải:
\(\begin{array}{l}
1,\\
{6.9^x} - {13.6^x} + {6.4^x} = 0\\
\Leftrightarrow 6.\frac{{{9^x}}}{{{4^x}}} - 13.\frac{{{6^x}}}{{{4^x}}} + 6 = 0\\
\Leftrightarrow 6.{\left( {\frac{3}{2}} \right)^{2x}} - 13.{\left( {\frac{3}{2}} \right)^x} + 6 = 0\left( 1 \right)\\
t = {\left( {\frac{3}{2}} \right)^x}\,\,\,\left( {t > 0} \right)\\
\left( 1 \right) \Leftrightarrow 6{t^2} - 13t + 6 = 0 \Rightarrow {t_1}.{t_2} = \frac{6}{6} = 1\\
\Rightarrow {\left( {\frac{3}{2}} \right)^{{x_1}}}.{\left( {\frac{3}{2}} \right)^{{x_2}}} = 1\\
\Leftrightarrow {\left( {\frac{3}{2}} \right)^{{x_1} + {x_2}}} = 1 \Rightarrow {x_1} + {x_2} = 0\\
2,\\
{3.8^x} + {4.12^x} - {18^x} - {2.27^x} = 0\\
\Leftrightarrow 3.\frac{{{8^x}}}{{{{27}^x}}} + 4.\frac{{{{12}^x}}}{{{{27}^x}}} - \frac{{{{18}^x}}}{{{{27}^x}}} - 2 = 0\\
\Leftrightarrow 3.{\left( {\frac{2}{3}} \right)^{3x}} + 4.{\left( {\frac{2}{3}} \right)^{2x}} - {\left( {\frac{2}{3}} \right)^x} - 2 = 0\\
\Leftrightarrow \left[ \begin{array}{l}
{\left( {\frac{2}{3}} \right)^x} = \frac{2}{3}\\
{\left( {\frac{2}{3}} \right)^x} = - 1\,\,\left( {VN} \right)
\end{array} \right. \Rightarrow x = 1
\end{array}\)
