It may sound ridiculous but I can't find this anywhere on the web.
Thanks in advance
I dont know how to answer. I have two exercisses from a book both say to define the NOT version of the Inclusion-Exclusion principle for three subsest A1,A2,A3 of a set A.The second exercise wants a formula for for the number of elements in A that don't belong in A1,A2,A3,A4.And I can't find it