Harison ,
[tex3]2^{4x}=2^{2x}+12[/tex3]
[tex3](2^{2x})^2-2^{2x}-12=0[/tex3]
Trocando [tex3]2^{2x}=\text{K}[/tex3]
[tex3]\text{K}^2-\text{K}-12=0[/tex3]
[tex3]\text{K}=\frac{1+\sqrt{49}}{2}[/tex3]
[tex3]\text{K}=4[/tex3]
Destrocando:
[tex3]2^{2x}=4[/tex3]
[tex3]2^{2x}=2^2[/tex3]
[tex3]2x=2[/tex3]
[tex3]{\color{red}\boxed{x=1}}[/tex3]