Answer :

[tex]5^{log_5x}=x;\ D:x\in\mathbb{R^+}\\\\\\\\5^{log_5x}=a\\\\log_55^{log_5x}=log_5a\\\\log_5x\cdot log_55=log_5a\\\\log_5x=log_5a\iff x=a\Rightarrow5^{log_5x}=x[/tex]