x²＋y²－2xy＋2x－2y＋1 用分组分解法因式分解

x²＋y²－2xy＋2x－2y＋1
＝（x²-2xy+y²）+2(x-y)+1
=(x-y)²+2(x-y)+1
=(x-y+1)²