x的平方+2xy+y的平方-6x-6y+9=0求x+y

问题描述:

x的平方+2xy+y的平方-6x-6y+9=0求x+y

  ﹙x+y﹚²-6﹙x+y﹚+9=0
  ﹙x+y-3﹚²=0
  x+y-3=0
  x+y=3

x^2+2xy+y^2-6x-6y+9=0
(x^2+2xy+y^2)-6(x+y)+9=0
(x+y)^2-6(x+y)+9=0
(x+y-3)^2=0
x+y-3=0
x+y=3