log(12)27 把对数化成以2为底的对数,并且省略底数2 =log27/log12=log(3^3)/log(3*2^2)=3log3/(2+log3) log(12)27=a--->3log3/(2+log3)=a--->log3=2a/(3-a) log(6)16 =log(2^4)/log(2*3) =4/(1+log3) =4/[1+2a/(3-a)]...