Suppose that
where and are even integers, while and are odd integers.
Is it necessarily the case that and ?
Solutions
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Un contre-exemple simple est de prendre a=2, b=9, c=6 et d=3. On a bien ab=cd=18. Mais on a : a ≠ c et b ≠ d. L’affirmation est donc fausse.
Counter-example : .
