HW 15.3. Let bn be the number of compositions of an n-element set in which every block has an odd...
Let Bn be the number of equivalence relations on the set n. Prove that Bn = Bn-k k-1 Let Bn be the number of equivalence relations on the set n. Prove that Bn = Bn-k k-1
Problem 7. (20 pts) Let n N be a natural number and X a finite set with n elements. Show that the number of permutations of X such that no element stays in the same position is n. n! k! For instance, there are 6-3! permutations of 3 elements, but only 2 of them are permutations which fix no element. Similarly, there are 24 41 permutations of 4 elements, but only 9 which fix no element Hint: Use the Inclusion-Erclusion...
8.3.1 Prove the following: (a) Every infinite series of the form 0O 72 (8.2) using appropriate choices for the coefficients Ibn], with the restrictioin that either bn- 0 or bn 1 is true for every n, represents a number in the interval [0, 1), with the exception that if bn n then the sum of the series is exactly 1. (b) Every real number in the interval [0,1) can be represented using a binary expansion, that is, can be represented...
3. a. Let H be a subgroup of a commutative group G. If every element h ∈ H is a square in H (i.e., h = k 2 for some k ∈ H), and every element of G/H is a square in G/H, then every element of G is a square in G. b. Let G be a group and H a subgroup with [G : H] = 2. If g ∈ G has odd order (i.e., ord(g) is odd),...
A 13. Let X be a p-element set and let Y be a k-element set. Prove that the number of functions f :X >Y which map X onto Y equals k!S(p, k) S#(p, k) : A 13. Let X be a p-element set and let Y be a k-element set. Prove that the number of functions f :X >Y which map X onto Y equals k!S(p, k) S#(p, k) :
Problem 4. Let p be an odd prime, and let Tp C Zp denote the set of elements of Zp which are perfect cubes: Tp-(a: a E z;} (1) Show that if p1 (mod 3) then Tp (p 1)/3. Problem 4. Let p be an odd prime, and let Tp C Zp denote the set of elements of Zp which are perfect cubes: Tp-(a: a E z;} (1) Show that if p1 (mod 3) then Tp (p 1)/3.
Let Ga finite abelian group. Prove that a)If pa primenumber divides G|, G has an element of order p b)If G2n with n odd, G has exactly oneelement with order 2 Let Ga finite abelian group. Prove that a)If pa primenumber divides G|, G has an element of order p b)If G2n with n odd, G has exactly oneelement with order 2
What is the number of subsets of a set with n elements, containing a given element? the textbook answer is 2^(n-1), why do we subtract the given element?
Problem 7. (20 pts) Let n EN be a natural nmber and X a finite set with n elements. Show that the number of permutations of X such that no element stays in the same position is n! k! k o For instance, there are 6 = 3! permutations of 3 elements, but only 2 of them are permutations which fix no element. Similarly, there are 24-4! permutations of 4 elements, but only 9 which fix no element. Hint: Use...
Use induction to prove that every set of n elements has 2n distinct subsets, for all n ? 0. Hint for the inductive case: fix some element of the set and consider whether it belongs to the subset or not. In either case, reduce to the inductive hypothesis.