x的平方+2xy+y的平方—2x—2y+1=0
(x+y)^2-2(x+y)+1=0
(x+y-1)^2=0
x+y-1=0
x+y=1为什么(x+y-1)^2=0套用完全平方公式得来的a^2-2ab+b^2=(a-b)^2(x+y)^2-2(x+y)+1^2=0(x+y-1)^2=0x+y-1=0x+y=1这个过程能说仔细点么(x+y)^2-2(x+y)+1^2=0(x+y-1)^2=0套用完全平方公式得来的a^2-2ab+1^2=(a-1)^2(x+y)^2-2(x+y)+1^2=0(x+y-1)^2=0x+y-1=0x+y=1