a+b+c=0,-(a+b)=c,-(b+c)=a,-(a+c)=b,代入：a2/2a2+bc+ b2/2b2+ac + c2/2c2+ab=a²／[2a²－b﹙a＋b﹚]＋b²／[2b²－c﹙b＋c﹚]＋c²／[2c²－a﹙a＋c﹚]=a²／[﹙2a＋b﹚﹙a－b﹚]＋b...