Could you tell me how to write a very formal proof of the statment below with the contrapositive methode, if possible.(adsbygoogle = window.adsbygoogle || []).push({});

(I know how to do it with contradiction)

Let x be a rational number and y an irrational number, then x times y is irrational.

Sincerely,

V. Uljanov

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# Proving with contrapositive methode instead of contradition

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