若x²+xy+5y=3,y²+xy+5x=-3,求x+y旳值
人气：422 ℃ 时间：2019-11-07 00:25:49
解答
x²＋xy＋5y＝3……………………① y²＋xy＋5x＝﹣3.………………②①＋②得：x²＋2xy＋y²＋5x＋5y＝0 ﹙x＋y﹚²＋5﹙x＋y﹚＝0 ﹙x＋y﹚﹙x...
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