已知a²-a-4=0,求a²-2﹙a²-a+3﹚-½﹙a²-a-4﹚-a的值

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已知a²-a-4=0,求a²-2﹙a²-a+3﹚-½﹙a²-a-4﹚-a的值

a²-2﹙a²-a+3﹚-½﹙a²-a-4﹚-a
=a²-2(a²-a-4+7)-0-a
=a²-2(0+7)-a
=a²-a-4-10
=-10;