我中午要~~~~11点半之前要~~下午要去上课~~大家帮帮忙~~
热心网友
a=lg10/lg3=1/lg3lg3=1/ab=lg25/lg6=(lg100-lg4)/(lg2+lg3)=(2-2lg2)/(lg2+lg3)(2+b)lg2=2-blg3lg2=(2-b/a)/(b+2)log4$45=lg45/lg4=(lg5+lg9)/2lg2=(1-lg2+2lg3)/2lg2代入可得：log4$45=(ab+3b+4)/2(2a-b)
热心网友
log3(10)=a ,log6(25)=b ,求log4(45)因为log3(10)=a ,log6(25)=b所以lg2 + lg5 =a*lg3 , 2*lg5 =b*(lg2 +lg3)解得：b(a+1)*lg2 =(2a-b)*lg5 , b(a+1)*lg3=(2+b)*lg5所以log4(45)=(lg5 +2*lg3)/(2*lg2) = [b(a+1)*lg5 + 2b(a+1)*lg3]/[2b(a+1)*lg2 ]=[b(a+1)+ 2(2+b)]/[2(2a-b)]=(ab+3b+4)/(4a-2b)