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log29=a18b=5用ab表示log1845=

题目详情
log2 9 =a 18b=5用ab 表示log18 45=
▼优质解答
答案和解析
a=lg9/lg2=2lg3/lg2
lg3=alg2/2
log18 9
=lg9/lg18
=2lg3/(2lg3+lg2)
=alg2/(alg2+lg2)
=a/(a+1)
b=log18 5
所以log18 45
=log18 (9×5)
=log18 9+log18 5
=a/(a+1)+b
=(a+ab+b)/(a+1)