Sets and Operations on Sets

Mathematics — First Preparatory

Common mistakes

Confusing membership ∈ with subset ⊆. An element belongs to a set, while a subset is a set inside another set.
Forgetting that the empty set ∅ is a subset of every set. It is not “nothing”.
Writing intersection when union is asked, or the other way round. The symbol ∩ means common.
When counting n(A ∪ B), forgetting to subtract n(A ∩ B), which gives a number that is too large.
Confusing A − B with B − A. These are usually different sets.

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