设x，y满足约束条件，若目标函数z=ax+by（a＞0，b＞0）的最大值为12， 则的最小值为

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SQL Error: select id,body,options from ***_enewstiku_ where sourceid='15531' and id < 2638689 and id<>'2638689' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku_ where sourceid='15531' and id > 2638689 and id<>'2638689' order by id asc limit 5