已知log2 3=a,3^b=7,求log12 56.
题目
已知log2 3=a,3^b=7,求log12 56.
答案
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)
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