[tex]\large\boxed{\begin{array}{l}(\bf{UNIRIO})\,\sf Se\,x=\ell og_32,ent\tilde ao\, 3^x+3^{-x}\,\acute e\,igual\,a:\\\underline{\sf soluc_{\!\!,}\tilde ao\!:}\\\rm x=\ell og_32\iff 3^x=2\\\rm 3^x+3^{-x}=3^x+(3^x)^{-1}\\\rm 3^x+3^{-x}=2+2^{-1}\\\rm 3^x+3^{-x}=2+\dfrac{1}{2}\\\\\rm 3^x+3^{-x}=\dfrac{4+1}{2}\\\\\rm 3^x+3^{-x}=\dfrac{5}{2}\end{array}}[/tex]
