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Can someone please explain how to do this problem?

Prove or disprove the statement “If $a \mid b$ and $c \mid d$, then $(a + c)\mid(b + d)$”.

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    Experimentation with such things can be very important, both in a search for a counterexample and a search for a proof. In your case, in seconds you will find a counerexample.2012-10-03

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