Question

Se $2^{x-1} + 2^{x}+ 2^{x+2} = \frac{11}{4}$, então x é igual a:

a) 3
b)-2
c)-1
d)1
e)0

Answer 1

$2^{x-1} + 2^x + 2^{x+2} = \frac{11}{4}\\ \\2^x + 2.2^x + 8.2^x = \frac{11}{2}\\ \\11.2^x = \frac{11}{2}\\ \\ 2^x= \frac{1}{2} \\\\ 2^x= 2^{-1}\\ \\x=-1$