log2 9 =a 18b=5用ab 表示log18 45=
问题描述：
log2 9 =a 18b=5用ab 表示log18 45=
答
a=lg9/lg2=2lg3/lg2lg3=alg2/2log18 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)