4log2(u)-3 >= log²2(u)
log²2(u)-4log2(u)+3 <= 0
log2(u) = t
t²-4t+3 <= 0
t²-t-3t+3 <= 0
t(t-1)-3(t-1) <= 0
(t-1)(t-3) <= 0
+. -. +
[1][3]
1 <= t <= 3
1 <= log2(u) <= 3
2¹ <= 2^log2(u) <= 2³
2 <= u <= 8
u€[2; 8]
