. , , , , , .. , - 3 A = {a; b; c} , , A = {a : P(a)} , . .
, , , . 3 {1,2,3,4} ( ), , .. , x ( ){1, 2,3} {1,2,3,4}
, {}, , . , U , , . S . |S| , , , A = { : } = {1,2,3,4, 5} =
{1,3,5,7,9}, = {1,3,5}. , , . = { : } = {1,2,6,7}, = {2,3,5,6}, =
{1,2,3,5,6,7}
- , . = { : } = {1,2,4,6,7}, = {2,3,4, 5,6}, - = {1,7} , ,
(-){-) = {1,2,4,6,7}, = {2,3,4, 5,6}, = {1, 3, 5,7}
? 2 ? , n ?
. . . : . . . : - "", 2004. . , . . . , ,
2012http://ru.wikipedia.org
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