原式可化为logax+ 3 logax - logay logax =3,即logay=loga2x-3logax+3=(logax- 3 2 )2+ 3 4 ,知当logax= 3 2 时,logay有最小值 3 4 .∵0<a<1,∴此时y有最大值a 3 4 .根据题意a 3 4 = 2 4 ?a= 1 4 .这时x=a 3 2 =( 1 4 ) 3 2 = 1 8 .