Assume x = y.
Multiply by x on the both sides: x
2 = xy

Subtract y
2
from both sides: x
2 − y
2 = xy − y
2
Factorize both sides: (x + y)(x − y) = y(x − y)
Divide by x + y on both sides: x + y = y
Since x = y, then 2y = y.
Divide by y both sides: 2=1
Since 2 ≠ 1, What went wrong in the steps above?