Đáp án:
$\begin{array}{l}
g){3^{x + 2}} + {3^{x + 1}} - {2.3^x} = 11\\
\Rightarrow {3^x}{.3^2} + {3^x}{.3^1} - {2.3^x} = 11\\
\Rightarrow {9.3^x} + {3.3^x} - {2.3^x} = 11\\
\Rightarrow {10.3^x} = 11\\
\Rightarrow {3^x} = \dfrac{{11}}{{10}}\\
\Rightarrow \text{không có x thỏa mãn}\\
h)2\left( {x + 3} \right) + 5x = 55\\
\Rightarrow 2x + 6 + 5x = 55\\
\Rightarrow 7x = 55 - 6\\
\Rightarrow 7x = 49\\
\Rightarrow x = \dfrac{{49}}{7}\\
\Rightarrow x = 7\\
\text{Vậy}\,x = 7\\
n)\left( {x - 1} \right) \in U\left( {3x + 5} \right)\\
\Rightarrow \left( {3x + 5} \right) \vdots \left( {x - 1} \right)\\
Do:3x + 5\\
= 3x - 3 + 8\\
= 3\left( {x - 1} \right) + 8\\
3\left( {x - 1} \right) \vdots \left( {x - 1} \right)\\
\Rightarrow 8 \vdots \left( {x - 1} \right)\\
\Rightarrow \left( {x - 1} \right) \in \left\{ { - 8; - 4; - 2; - 1;1;2;4;8} \right\}\\
\Rightarrow x \in \left\{ { - 7; - 3; - 1;0;2;3;5;9} \right\}\\
Do:x \ge 0\\
\Rightarrow x \in \left\{ {0;2;3;5;9} \right\}
\end{array}$
