Question

请问这道数学题是否是这样做?

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

Answer 1

应该移项,即
x^2-y^2=(x-y)
x^2-y^2-（x-y）=0
(x+y)(x-y)-(x-y) =0
（x-y）（x+y-1）=0
故x-y=0，或x+y-1=0
即x=y或x+y=1

Answer 2

(x+y)(x-y)=x-y
x+y=1或x=y

Answer 3

x^2-y^2=(x-y)
(x+y)(x-y)=(x-y)
x^2-y^2=(x-y)
(x+y)(x-y)-(x-y)=0
(x+y-1)(x-y)=0
故x+y=1或x=y