. (1878), , À0, , .
U, , . , U = {, , , , , , , , }. , , . . . U W, . , , (. . ), , . , , . .
, : = . , 4- 8 = 16, /15 = 2/5 5-3 = 125, 6.
, . 2 = 1 = {(-1)k, k = 0, 1, 2,...}. , , - . , 2 + 1 = 0 : {| 2 + 1 = 0, } = 0, = i, = - i: {|2 + 1 = 0, } = { i, -i }.
, . , A = . .
| | (). , 0: n() = 0, n(U) = 9 |U| = 9.
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1. ={1, 2, 3,...,10}, B = {2, 4, 6, 8, 10}. / , .
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