Search results for set-theory&algebra

23 votes
2 answers
42
41 votes
5 answers
47
How many onto (or surjective) functions are there from an $n$-element $(n ≥ 2)$ set to a $2$-element set?$ 2^{n}$$2^{n} – 1$$2^{n} – 2$$2(2^{n} – 2)$
27 votes
4 answers
49
Consider the set $S = \{1, ω, ω^2\}$, where $ω$ and $ω^2$ are cube roots of unity. If $*$ denotes the multiplication operation, the structure $(S, *)$ formsA GroupA R...
41 votes
3 answers
51
43 votes
2 answers
55
The number of possible commutative binary operations that can be defined on a set of $n$ elements (for a given $n$) is ___________.
29 votes
8 answers
58
If $P, Q, R$ are subsets of the universal set U, then $$(P\cap Q\cap R) \cup (P^c \cap Q \cap R) \cup Q^c \cup R^c$$ is$Q^c \cup R^c$$P \cup Q^c \cup R^c$$P^c \cup Q^c \c...