则|a+b|﹣|a﹣b|﹣|a|+|b|
=﹣a﹣b﹣a+b﹣a﹣b
=﹣3a﹣b.
①教育是民族振兴的基石
②百年大计教育为本
③科技是第一生产力
④教育是社会进步的基石
To our surprise, all the l____ on the tree were eaten up by the cow soon.