已知log以5为底6的对数=a,log以5为底4的对数=b.用a.b表示log以25为底12的对数

log(5)(6)=alog(5)(2)+log(5)(3)=alog(5)(4)=b2log(5)(2)=blog(5)(2)=b/2b/2+log(5)(3)=a解得log(5)(3)=a-b/2log(25)(12)=log(25)(3)+log(25)(4)=log(5²)(3)+log(5²)(2²)=(1/2)log(5)(3)+log(5)(2)=(1/2)*(a-b/2)+b/2=a/2-b/4+b/2=a/2+b/4