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∵x2+xy+y=14①,y2+xy+x=28②,∴①+②,得:x2+2xy+y2+x+y=42,∴(x+y)2+(x+y)-42=0,∴(x+y+7)(x+y-6)=0,∴x+y+7=0或x+y-6=0,解得:x+y=-7或x+y=6.
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