$\text{$9^{x}$ =81.(27+$9^{15}$ ): ($3^{5}$ +$3^{32}$ )}$
$\text{=81.(3³+$3²^{15}$ ): [$3^{5}$.(1+$3^{27}$)]}$
$\text{=81.(3³+$3^{30}$):[$3^{5}$.(1+$3^{27}$)]}$
$\text{=81.3³.(1+$3^{27}$):[$3^{5}$.(1+$3^{27}$)]}$
$\text{=81.3³:$3^{5}$}$
$\text{=$3^{7}$:$3^{5}$}$
$\text{=9}$
$\text{Nên $9^{x}$=9}$
$\text{⇒x=1}$