Đáp án: x=0 hoặc x=1
Giải thích các bước giải:
$\begin{array}{l}
b){3^{{x^2} + x}} - {9.3^{{x^2} - x}} - {3^{2x}} + 9 = 0\\
\Rightarrow \left( {{3^{{x^2} + x}} - {3^{2x}}} \right) + \left( { - {{9.3}^{{x^2} - x}} + 9} \right) = 0\\
\Rightarrow \left( {{3^{{x^2} - x + 2x}} - {3^{2x}}} \right) - 9\left( {{3^{{x^2} - x}} - 1} \right) = 0\\
\Rightarrow \left( {{3^{{x^2} - x}} - 1} \right){.3^{2x}} - 9.\left( {{3^{{x^2} - x}} - 1} \right) = 0\\
\Rightarrow \left( {{3^{{x^2} - x}} - 1} \right).\left( {{3^{2x}} - 9} \right) = 0\\
\Rightarrow \left[ \begin{array}{l}
{3^{{x^2} - x}} = 1\\
{3^{2x}} = 9
\end{array} \right. \Rightarrow \left[ \begin{array}{l}
{x^2} - x = 0\\
2x = 2
\end{array} \right. \Rightarrow \left[ \begin{array}{l}
x = 0\\
x = 1
\end{array} \right.
\end{array}$
