由log1/2(1-3x)=-log2(1-3x)可知:
移项得log2(2x-1)+log2(1-3x)>0
即log2((2x-1)*(1-3x))=log2(5x-6x^2-1)>0
即5x-6x^2-1>1
6x^2-5x+21!