Question

η(AυB)=η(A)+η(B)-η(ΑηΒ)​

Answer 1

Answer:

it is a question from set indicating that at lhs we have to count number of elements in A B eg a = 1 2 3 and B =3 4 5

so answer is 1 2 3 4 5 and second indicates number of element in a and in subtracted by a Πb