Inclusion-exclusion principle (need some help)

Revision en1, by muzzaleeni, 2020-02-28 18:21:35

The inclusion-exclusion principle can be expressed as follows:

To compute the size of a union of multiple sets, it is necessary to sum the sizes of these sets separately, and then subtract the sizes of all pairwise intersections of the sets, then add back the size of the intersections of triples of the sets, subtract the size of quadruples of the sets, and so on, up to the intersection of all sets. The above definition can be expressed mathematically as follows:

It is intuitive for $$$n\leq 3$$$. But I have some problem with it. I cannot understand why it is like that?! (previously thanks!)

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  Rev. Lang. By When Δ Comment
ru1 Russian muzzaleeni 2020-02-28 19:40:55 725 Первая редакция перевода на Русский
en1 English muzzaleeni 2020-02-28 18:21:35 725 Initial revision (published)