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| collection of objects in which the ordering is not important and we won't consider repeated elements as being distinct from one another |
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| the number of elements in A (size). |A| |
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| is a set AND every element in the subset is also an element of the original set |
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| the power set of S is the set of all subsets of the set S. They have to be 2^n |
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| elements that are in either A or B but not in both. |
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| elemets that are in A but not in B |
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| f:A-->B is injective (one-to-one) provided each x gets exactly one y AND each y gets exactly one x |
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| f:A-->B is called surjective ("onto") provided each element in the co-domain B has a pre-image element in the domain.. there's a least one x for each y |
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| Given gcd(a,b)=d, then the equation ax+by=w has integer solutions x,y iff.. |
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| the inverse (x^-1) of x in mod n |
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| in modn with n>2, an element is invertible iff |
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| a function which is both injective and surjective |
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