[tex]1+5^{x}-2\cdot 25^x=0\\
-2\cdot (5^x)^2+5^x+1=0\\
Notam\ 5^x=t,t\ \textgreater \ 0\\
-2t^2+t+1=0\\
\Delta=1+8=9\Rightarrow \sqrt{\Delta}=3\\
t_1=\dfrac{-1+3}{-4}=-\dfrac{1}{2}\ \textless \ 0\\
t_2=\dfrac{-1-3}{-4}=1\\
5^{x}=1\Rightarrow x=0(sol. unica))[/tex]
