Let a be an element of a finite group G. The order of a is the
least power k such that ak = e.
Find the orders of following elements in S5
a. (1 2 3 )
b. (1 3 2 4)
c. (2 3) (1 4)
d. (1 2) (3 5 4)
Let G be a group and a be an element of G. Let φ:Z→G be a map
defined by φ(n) =a^{n} for all n∈Z. a)Show that φ is a group
homomorphism. b) Find the image ofφ, i.e.φ(Z), and prove that it is
a subgroup ofG.
Let G be a group, and let a ∈ G be a fixed element. Define a
function Φ : G → G by Φ(x) = ax−1a−1.
Prove that Φ is an isomorphism is and only if the group G is
abelian.
Let G be a group of order 42 = 2 * 3 * 7
(a) Let P7 be a Sylow 7-subgroup of G and let P3 be a Sylow
3-subgroup of G . What are the orders of P3 and P7?
(b) Prove that P7 is the unique Sylow 7-subgroup of G and that
P7 is normal.
(c) Prove that P3P7 is a subgroup of G
(d) Prove that P3P7 is a normal subgroup of G .
(e) Let P2...
Let G be a cyclic group generated by an element a.
a) Prove that if an = e for some n ∈ Z, then G is
finite.
b) Prove that if G is an infinite cyclic group then it contains
no nontrivial finite subgroups. (Hint: use part (a))
Let B be a finite commutative group without an element of order
2. Show the mapping of b to b2 is an automorphism of B. However, if
|B| = infinity, does it still need to be an automorphism?
Let G be a nonabelian group of order 253=23(11), let P<G be a
Sylow 23-subgroup and Q<G a Sylow 11-subgroup.
a. What are the orders of P and Q. (Explain and include any
theorems used).
b. How many distinct conjugates of P and Q are there in G? n23?
n11? (Explain, include any theorems used).
c. Prove that G is isomorphic to the semidirect product of P and
Q.
Let G be a group of order p
am where p is a prime not dividing m. Show the following
1. Sylow p-subgroups of G exist; i.e. Sylp(G) 6= ∅.
2. If P ∈ Sylp(G) and Q is any p-subgroup of G, then there exists g
∈ G such that Q 6
gP g−1
; i.e. Q is contained in some conjugate of P. In particular, any
two Sylow p-
subgroups of G are conjugate in G.
3. np ≡...