2的a次方=3 a=log2(3)
2的b次方=6 b=log2(6)=log2(2*3)=log2(2)+log2(3)=1+log2(3)
2的c次方=12 c=log2(12)=log2(3*2*2)=2+log2(3)
显然
a+c=2b