Man I've become desperate. I just signed up needing help on this homework. Can anyone help me with these two problems?(adsbygoogle = window.adsbygoogle || []).push({});

Let A be the set {1,2,3,4}. Prove that a relation R on A with 15 ordered pairs is not transitive.

I've got no clue on that one.

And this second one, which I know the proof, but I need some help wording it correctly:

If f is injective (one-to-one) and C subset D are any subsets of A, then f(D-C) = f(D) - f(C).

I know the proof, but every time I try and word it, it just sounds wrong.

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# Abstract math help if possible

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