# Is this correct(proof)?

I figured it out.

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If x is any real number? I'd choose a number more interesting than $$x=\pi$$. Remember that the claim employs "either/or", so if both $$\pi - x$$ and $$x+\pi$$ are irrational the claim is false.

So the proof is incorrect because the statement is false? How do you know its an exclusive or?

Yes. Give a counterexample to disprove the claim. It's an exclusive or because that's the language you use when it's an exclusive or. EITHER x-pi is irrational OR x+pi is irrational is what the claim is for any real x, so if they're both irrational then that isn't "either", that's "both".

If you changed it to either A... or...B, or both, then the statement and proof would be true?

well strictly speaking just dropping "either" would work, but nobody ever uses "or" to mean logical or. But yes what you say is right.

Edit: Yeah Cristo is right I had totally forgotten about any "proof" by the time I wrote this.

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cristo
Staff Emeritus