换底：log18(2)=log2(2)/log2(18)=1/2log2(3)=a
所以log2(3)=1/2a为什么log2(2)/log2(18)=1/2log2(3)log2(18)=log2(3²)=2log2(3)3²=9不等于18log2(18)=log2(2×3²)=1+2log2(3)所以答案是1/2a-1/2吗？对的