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# Has anyone ever seen a proof of 1+1=3?

### 4 Answers

- Anonymous1 decade agoFavorite Answer
In college, I took a course in mathematical analysis. It was without doubt the most tedious mathematics course I ever took in my life. The hightlight of the course came about 2/3 of the way into it, when - yes! - we learned a proof that 1 + 1 = 2. Man, was that ever a big moment!

So, don't try to convince me that 1 + 1 is something other than 2, 'cause I've seen the proof!

- PuggyLv 71 decade ago
No, but I have seem a "proof" that 1 = 2.

There is no actual proof that 1 = 2. If 1 were really equal to 2, the mathematical foundation would crumble.

Here is the false proof that 1 = 2.

Let x = 1 and y = 1. Then

x = y. Multiply both sides by x,

x^2 = xy. Subtract y^2 both sides,

x^2 - y^2 = xy - y^2. Factor both sides,

(x - y)(x + y) = y(x - y). Cancel the common term of (x - y) on both sides.

x + y = y

Resubstitute x = 1 and y = 1

1 + 1 = 1

2 = 1

The only reason why this appears to work is because of an invalid step. Nevertheless, this is the false proof.

- JediLv 41 decade ago
I could prove to you that .9 repeating is one, but that is because it is.

1+1=3 only in some different weird systems, like in modulo 1. But those are different number systems practically.

What you are talking about is correct. 1+1=2 always.