1、⑴3﹙x+y﹚²-7﹙x+y﹚-9﹙x+y﹚²-6﹙x-y﹚ 解:3﹙x+y﹚²-7﹙x+y﹚-9﹙x+y﹚²-6﹙x-y﹚ =-6﹙x+y﹚²-7-7﹙x+y﹚-6﹙x-y﹚ ⑵3﹙a-b﹚+6﹙a+b﹚-2﹙a+b﹚+4﹙a-b﹚ 解:3﹙a-b﹚+6﹙a+b﹚-2﹙a+b﹚+4﹙a-b﹚ =7(a-b)+4(a+b) 2、己知a+b=2,求多项式1/4﹙a+b﹚²-9﹙a+b﹚-1/2﹙a+b﹚²+
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