log2 12=log2 (3*4)=log2 3+2
log2 3
log3 9=2
log27 64=log3 4=2log3 2
原式=1+（2/log2 3)+2-2log3 2
=3+2(1/log2 3-log3 2)
=3
注1/log2 3=log3 2