log2(4x)=log2(4)+log2(x)=2+log2(x);同理log2(2x)=log2(2)+log2(x)=1+log2(x)设t=log2(x),则y=(2+t)(1+t) 因为1/4 ≤ x ≤ 4,所以-2 ≤ log2(x) ≤ 2,即-2 ≤ t ≤ 2y=t^2+3t+2 2 ≤ t ≤ 2到这步应该会了吧,简单的...