[tex]16^x=13\implies (2^4)^x=13\implies ((2^2)^2)^x=13\implies ((4)^2)^x=13 \\\\\\ 4^{2\cdot x}=13\implies 4^{x\cdot 2}=13\implies \left[4^x \right]^2=13\implies \boxed{4^x}=\sqrt{13} \\\\[-0.35em] ~\dotfill\\\\ 2^{2x+1}\implies 2^{2x}\cdot 2^1\implies (2^2)^x\cdot 2\implies 4^x\cdot 2\implies \boxed{\sqrt{13}}\cdot 2\implies 2\sqrt{13}[/tex]
