math tard, Help

[answer-is-42]

Where is the flaw in this? Think it is division by 0 but not sure.

x=y
x squared = xy
x squared-y squared = xy-y squared
(x+y) (x-y)=y(x-y)
(x+y) (x-y)/(x-y)=y(x-y)/(x-y)
(x+y)=y

OF COURSE ITS THE DIVIDE BY ZERO (x-y)=0.
I use this trick all the time with people who think a logical proof means anything in reality.
The next steps by the way is 2y=y so 2=1