0\\t^2+2t-80=0\\D=4+320=324=18^2\\t_1=\frac{-2+18}{2}=8\\t_2=\frac{-2-18}{2}=-10" alt="2^{x+1}+4^x=80\\2^{2x}+2^x*2-80=0\\\\2^x=t,\ t>0\\t^2+2t-80=0\\D=4+320=324=18^2\\t_1=\frac{-2+18}{2}=8\\t_2=\frac{-2-18}{2}=-10" align="absmiddle" class="latex-formula">
t₂ ∉ t>0 - исключаем.