Problem 1E: Find all generators of Z6,Z8,andZ20 . Problem 2E: Suppose that a,b,andc are cyclic groups of orders 6, 8, and20, respectively. Find all generators of... Problem 3E: List the elements of the subgroups 20and10inZ30 . Let a be agroup element of order 30. List the... Problem 4E: List the elements of the subgroups 3and15inZ18 . Let a be agroup element of order 18. List the... Problem 5E: List the elements of the subgroups 3and7inU(20) . Problem 6E: What do Exercises 3, 4, and 5 have in common? Try to make a generalization that includes these three... Problem 7E: Find an example of a noncyclic group, all of whose proper subgroupsare cyclic. Problem 8E: Let a be an element of a group and let a=15 . Compute the ordersof the following elements of G. a.... Problem 9E Problem 10E: In Z24 , list all generators for the subgroup of order 8. Let G=aandleta=24 . List all generators... Problem 11E: Let G be a group and let aG . Prove that a1=a . Problem 12E: In Z, find all generators of the subgroup 3 . If a has infinite order,find all generators of the... Problem 13E: In Z24 , find a generator for 2110 . Suppose that a=24 . Finda generator for a21a10 . In general,... Problem 14E: Suppose that a cyclic group G has exactly three subgroups: G itself,{e}, and a subgroup of order 7.... Problem 15E: Let G be an Abelian group and let H=gG||g divides 12}.Prove that H is a subgroup of G. Is there... Problem 16E: Complete the statement: a|=|a2 if and only if |a| . . . . Problem 17E: Complete the statement: a2|=|a12 if and only if . . . . Problem 18E: Let a be a group element and a= . Complete the followingstatement: ai=aj if and only if . . . . Problem 19E: If a cyclic group has an element of infinite order, how many elementsof finite order does it have? Problem 20E: Suppose that G is an Abelian group of order 35 and every elementof G satisfies the equation x35=e .... Problem 21E: Let G be a group and let a be an element of G. a. If a12=e , what can we say about the order of a?... Problem 22E: Prove that a group of order 3 must be cyclic. Problem 23E: Let Z denote the group of integers under addition. Is every subgroupof Z cyclic? Why? Describe all... Problem 24E: For any element a in any group G, prove that a is a subgroup ofC(a) (the centralizer of a). Problem 25E: If d is a positive integer, d2 , and d divides n, show that the numberof elements of order d in Dn... Problem 26E: Find all generators of Z. Let a be a group element that has infiniteorder. Find all generators of a... Problem 27E: Prove that C*, the group of nonzero complex numbers under multiplication,has a cyclic subgroup of... Problem 28E: Let a be a group element that has infinite order. Prove that ai=aj if and only if i=j. Problem 29E: List all the elements of order 8 in Z8000000 . How do you know your listis complete? Let a be a... Problem 30E: Suppose that G is a group with more than one element. If the onlysubgroups of G are {e} and G, prove... Problem 31E: Let G be a finite group. Show that there exists a fixed positive integern such that an=e for all ain... Problem 32E: Determine the subgroup lattice for Z12 . Generalize to Zp2q , where pand q are distinct primes. Problem 33E: Determine the subgroup lattice for Z8 . Generalize to Zpn , where p isa prime and n is some positive... Problem 34E: Prove that a finite group is the union of proper subgroups if andonly if the group is not cyclic. Problem 35E: Show that the group of positive rational numbers under multiplicationis not cyclic. Why does this... Problem 36E: Consider the set {4, 8, 12, 16}. Show that this set is a group undermultiplication modulo 20 by... Problem 37E: Give an example of a group that has exactly 6 subgroups (includingthe trivial subgroup and the group... Problem 38E: Let m and n be elements of the group Z. Find a generator for thegroup mn . Problem 39E: Suppose that a andb are group elements that commute. If |a| is Finiteand |b| infinite, prove that... Problem 40E Problem 41E Problem 42E: Let F and F’be distinct reflections in D21 . What are the possibilitiesfor |FF’|? Problem 43E: Suppose that H is a subgroup of a group G and H=10 . If abelongs to G and a6 belongs to H, what are... Problem 44E Problem 45E: If G is an infinite group, what can you say about the number ofelements of order 8 in the group?... Problem 46E: If G is a cyclic group of order n, prove that for every element a in G, an=e . Problem 47E: For each positive integer n, prove that C*, the group of nonzerocomplex numbers under... Problem 48E: Prove or disprove that H=nZn is divisible by both 8 and 10}is a subgroup of Z. What happens if... Problem 49E Problem 50E Problem 51E Problem 52E Problem 53E Problem 54E Problem 55E Problem 56E Problem 57E Problem 58E Problem 59E: Prove that no group can have exactly two elements of order 2. Problem 60E: Given the fact that U(49) is cyclic and has 42 elements, deduce thenumber of generators that U(49)... Problem 61E: Let a andb be elements of a group. If a=10andb=21 , showthat ab={e} . Problem 62E: Let a andb belong to a group. If |a| and |b| are relatively prime,show that ab={e} . Problem 63E: Let a andb belong to a group. If a=24andb=10 , what are thepossibilities for ab ? Problem 64E: Prove that U(2n)(n3) is not cyclic. Problem 65E: Prove that for any prime p and positive integer n,(pn)=pnpn1 . Problem 66E: Prove that Zn has an even number of generators if n2 . What doesthis tell you about (n) ? Problem 67E: If a5=12 , what are the possibilities for |a|? If a4=12 , what arethe possibilities for |a|? Problem 68E: Suppose that x=n . Find a necessary and sufficient condition on rand s such that xrkxs . Problem 69E: Let a be a group element such that a=48 . For each part, find adivisor k of 48 such that a21=ak;... Problem 70E: Prove that H={[1n01]|nZ} is a cyclic subgroup of GL(2,R) . Problem 71E: Suppose that |a| and |b| are elements of a group and a andb commute.If a=5andb=16 , prove that ab=80... Problem 72E: Let a andb belong to a group. If a=12,b=22,andabe , prove that a6=b11 . Problem 73E: Determine (81),(60)and(105) where is the Euler phifunction. Problem 74E: If n is an even integer prove that (2n)=2(n) . Problem 75E: Let a andb belong to some group. Suppose that a=m,b=n ,and m and n are relatively prime. If ak=bk... Problem 76E: For every integer n greater than 2, prove that the group U(n21) is not cyclic. Problem 77E: (2008 GRE Practice Exam) If x is an element of a cyclic group oforder 15 and exactly two of... format_list_bulleted