Exponential difficulty

Question

I am finding it difficult to do the $(2(2^{-x})$ part of the problem below.

So far I have gotten $2^{x+1}$ to equal $2y$ and I cannot seem to find how to get $2(2^{-x})$

$2^{x+1} + 2(2^{-x}) -5 = 0$

$2^x = y$

solve for x