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Hi all, [whoever is listening :-]

i mod j means the good old remainder for i/j

Hope this clears things up,

Adam

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So, does x__=__y(mod6) mean the remainder of x/y is 6 ?

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Not quite. These are called congruences.

Basically,

a º b (mod n) means "a equals b modulo n" or, I guess, "a and b have the same remainder when divided by n"

You can do some neat things, like add, subtract and multiply from both sides and keep equality (division is another story). There is a lot more stuff, but i don't remember it all off hand. This is the first page to come from google when you search for "congruences".

When I took 74.213 (Discrete Math for Computer Scientists) I took congruences, and it makes proofs like "If x-y is even, then x^{2}-y^{2} is divisible by 4", "Every cube is of the form 9n, 9n+1, or 9n-1" and other divisibility problems a fair bit easier, at least computation-wise.