早教吧作业答案频道 -->数学-->
log1/27(1/7)=a,log1/3(1/5)=b,求log81(175)
题目详情
▼优质解答
答案和解析
log1/27(1/7)=a
lg(1/7)/lg(1/27)=a
-lg7/(-lg27)=a
lg7/lg3^3=a
lg7/3lg3=a
lg7=3a*lg3
log1/3(1/5)=b
lg(1/5)=lg(1/3)=b
lg5/lg3=b
lg5=blg3
log81(175)
=lg175/lg81
=lg(5*5*7)/lg(3^4)
=(2lg5+lg7)/4lg3 lg7=3a*lg3 lg5=blg3
=(2blg3+3alg3)/4lg3
=(3a+2b)/4
lg(1/7)/lg(1/27)=a
-lg7/(-lg27)=a
lg7/lg3^3=a
lg7/3lg3=a
lg7=3a*lg3
log1/3(1/5)=b
lg(1/5)=lg(1/3)=b
lg5/lg3=b
lg5=blg3
log81(175)
=lg175/lg81
=lg(5*5*7)/lg(3^4)
=(2lg5+lg7)/4lg3 lg7=3a*lg3 lg5=blg3
=(2blg3+3alg3)/4lg3
=(3a+2b)/4
看了log1/27(1/7)=a,...的网友还看了以下：