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# I will prove 1=0 ; spot the fallacy

Jesus Angeles
Ranch Hand
Posts: 2068
Let X = Y

Subtract both sides by Y

X-Y = Y-Y

Divide both sides by X-Y

X-Y Y-Y
--- = ---
X-Y X-Y

Simplify the equation
Left side is 1 since numerator and denomenator are the same.
Right side is 0 because the numerator is Y-Y which is 0.

Therefore,

1 = 0

David O'Meara
Rancher
Posts: 13459
Divide by zero After that, everything else is invalid.
We had an interesting 'discussion' on the effects of dividing by zero a while back, but I won't go looking for a link since it mostly revolved around one person saying computers should check for divide by zero errors, and the rest of us saying they should

Stan James
(instanceof Sidekick)
Ranch Hand
Posts: 8791
My dad used to prove 1==2 with some trick like that, but he filled the blackboards all the way around his classroom to do it.

Jesus Angeles
Ranch Hand
Posts: 2068
it was my father too who showed this to me.

i wont be surprised if i show this to my future children; at least to those interested in math.

Chetan Parekh
Ranch Hand
Posts: 3640
5=6