错了,是2x²＋y²＋2xy-2x＋1=0
即(x²+2xy+y²)+(x²-2x+1)=0
(x+y)²+(x-1)²=1
所以x+y=0,x-1=0
所以x+y=0
2x²＋y²＋2xy-2y＋2=0 求x＋y=（ ）
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