由题意,-3≤log1/2x≤-1/2
∴1/2≤㏒2x≤3
令㏒2x=a
∴y=(log2 x/2)(log2 x/4)=(a-1)(a-2)
=a^2-3a+2
∵1/2≤a≤3
∴-1/4≤y≤2
∴值域为[-1/4,2]