True or false: If N is a subgroup of a group G then the set of left cosets of N in G form a group by defining aN bN = abN for all left cosets aN and bN. Give a proof or a counterexample.
4. True or False. Label each of the following statements as true or false. If true, give a proof, if false, give a counterexample. (a) Every nontrivial subgroup of Q* contains some positive and some negative numbers (b) Let G be a finite group. Let a E G. If o(a) 5, then o(a1) 5. (c) Let G be a group and H a normal subgroup of G. If G is cyclic, then G/H is also cyclic. (d) Le t R...
5. Let N be a normal subgroup of a group G and G/N be the quotient group of all right cosets of N in G. Prove each of the following: (a) (2 pts) If G is cyclic, then so is G/N. (b) (3 pts) G/N is Abelian if and only if aba-16-? E N Va, b E G. (c) (3 pts) If G is a finite group, then o(Na) in G/N is a divisor of (a) VA EG.
(2) (a) Prove that the set G = {+1, £i} is a finite subgroup of the multi- plicative group CX of nonzero complex numbers, and that the set H = {E1} is a finite subgroup of {+1, £i}. (b) Compute the index of H in G. (c) Compute the set of left cosets G/H.
18. Let N be a normal subgroup of a finite group G, and let Nxi, . N be a for complete list of (disjoint) right cosets. Prove that, as sets, Nx, Nz all i and j Nz,
(5) Let G be a group, and let H be a subgroup of G. Define a relation ~ on G as follows: X~ · y if x-ly E H. Prove that this is an equivalence relation, and that the equivalence classes of the relation are the left cosets of H.
Let G be a finite group and let H be a subgroup of G. Show using double cosets that there is a subset T of G which is simultaneously a left transversal for H and a right transversal for H.
(5 points) Recall the Definition: A subgroup H of G is called a normal subgroup of G if gH = Hg for all g E G. If so, we write H G. Mark each of the following true T or false F (using the CAPITAL LETTER T or F. Recall that if a statment is not necessarily ALWAYS true, then it is false. - T ח 1. Every subgroup of (Zn, e) is normal. 2. The cyclic group (f) is...
Problem 3. Subgroups of quotient groups. Let G be a group and let H<G be a normal subgroup. Let K be a subgroup of G that contains H. (1) Show that there is a well-defined injective homomorphism i: K/ H G /H given by i(kH) = kH. By abuse of notation, we regard K/H as being the subgroup Imi < G/H consisting of all cosets of the form KH with k EK. (2) Show that every subgroup of G/H is...
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),...
Answer Question 5 . Name: 1. Prove that if N is a subgroup of index 2 in a group G, then N is normal in G 2. Let N < SI consists of all those permutations ơ such that o(4)-4. Is N nonnal in sa? 3. Let G be a finite group and H a subgroup of G of order . If H is the only subgroup of G of order n, then is normal in G 4. Let G...