log以18为底5的对数=a,记为 log(18)(5)=a18^b=2 两边取以18为底的对数,得 log(18)(2)=blog(45)(36)=log(18)(36)/log(18)(45) {换底公式}=log(18)(18*2) / log(18)(5* 9) =(log(18)(18)+log(18)(2)) / (log(18)(5) + ...