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disM/exercise-sep-2.txt
2025-09-02 17:00:02 +02:00

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U = {x € Z+ : x <= 10}, A = {x : x udda, x != 5}, B = {x : x primtal}.
Bestäm |A|, |B|, ¨A, ¨B, AuB, A↓uB, och A\B
A = {1, 3, 7, 9}
B = {2, 3, 5, 7}
|A| = 4
|B| = 4
¨A = {2, 4, 5, 6, 8, 10}
¨B = {1, 4, 6, 8, 9, 10}
AuB = {1, 2, 3, 5, 7, 9}
A↓uB = {3, 7}
A\B = {1, 9}
A"delt"B = {1, 2, 5, 9}
Beviska:
1) ¨A↓u(AuB) = B\A
2) (AuB)↓u¨(A↓uB) = (A↓u¨B)u(B↓u¨A)