Question

Sabendo se que 4^x+2=64, calcule o valor de 2^-x

Answer 1

4^x+2=64
4^x+2 = 4^3
x+2 = 3
x = 3-2
x = 1

 2^-x=
2^-1=
1/2
..

Answer 2

Olá Pablo.

$4^{x+2}= 65\\ (2^2)^{x+2}= 2^6 \\ 2x+4=6 \\ 2x=6-4 \\ 2x= 2\\ x= \frac{2}{2} \\\boxed{\boxed{ x= 1}}$

Agora  que encontramos o valor se x basta substituir e resolver:
$\boxed{2^{-x} = 2^{-1}= \boxed{\frac{1}{2}}}$