log9 12=a,12^b=5,用a,b表示log45 24

a=lg12/lg9
=(2lg2+lg3)/2lg3
2alg3=2lg2+lg3
lg3=2lg2/(2a-1)
b=lg5/lg12
=(1-lg2)/(2lg2+lg3)
2blg2+blg3=1-lg2
lg3=(1-lg2+2blg2)/b
2lg2/(2a-1)=(1-lg2+2blg2)/b
2blg2=2a-1+(2a-1)(2b-1)lg2
lg2=(1-2a)/(4ab-2a-4b+1)
lg3=-2/(4ab-2a-4b+1)
log45(24)
=lg24/lg45
=(3lg2+lg3)/(2lg3+1-lg2)
=(5-6a)/(4ab-4b-4)