因为log2^3=a,3^b=7,所以： log2^(3^b)=log2^7 即blog2^3=log2^7 log2^7=ab 则log12^56 =(log2^56)/(log2^12) =(log2^8 +log2^7)/(log2^4 +log2^3) =(3+ab)/(2+a)
