计算:(1);(2)已知x=+1,y=﹣1,求x2﹣xy+y2的值.
解:(1)原式=2﹣1+2﹣﹣×=﹣;(2)∵x=+1,y=﹣1,∴x+y=2,xy=3﹣1=2,∴x2﹣xy+y2=(x+y)2﹣3xy=12﹣3×2=12﹣6=6.
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