Question

x^2y^2-4xy+x^2+y^2+1=0,那么x+y=

Answer 1

x^2y^2-4xy+x^2+y^2+1=0

(x^2y^2-2xy+1)+(x^2-2xy+y^2)=0

(xy-1)^2+(x-y)^2=0

所以xy-1=0,x-y=0

得x=1,y=1或x=-1,y=-1

所以x+y=2或-2

好像不是因式分解.