log2(x) = t

t²+t-2 <= 0

t²+2t-t-2 <= 0

t(t+2)-1(t+2) <= 0

(t+2)(t-1) <= 0

+. -. +

-----------[-2]--------------[1]------------

-2 <= t <= 1

-2 <= log2(x) <= 1

2^(-2) <= 2^(log2(x)) <= 2^1

1/4 <= x <= 2

Ответ: [1/4; 2]