# Question: exercise 15 prove that if a and b are sets...

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Exercise 1.5. Prove that if A and B are sets satisfying the property that A \ B = B \ A, then it must be the case that A = B.

Exercise 1.6. Using definition (1.2.5) of the symmetric difference, prove that, for any sets A and B, A4B = (A ∪ B) \ (A ∩ B).

Exercise 1.7. Verify the second assertion of Theorem 1.3.4, that for any collection of sets {Ai}i∈I, \ i∈I Ai !c = [ i∈I A c i .