Let G and H be two groups, , & € Hom (G, H), and A C G be a nonempty subset. (a) Prove ((A)) = ( (A)). Here (A) denotes the subgroup generated by A. (b) Let E = {a € G : (a) = v (a)} . Prove E G.

Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
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Question
Let \( G \) and \( H \) be two groups, \( \phi, \psi \in \text{Hom}(G, H) \), and \( A \subset G \) be a nonempty subset.

(a) Prove
\[ \phi(\langle A \rangle) = \langle \phi(A) \rangle. \]

Here, \( \langle A \rangle \) denotes the subgroup generated by \( A \).

(b) Let
\[ E = \{ a \in G : \phi(a) = \psi(a) \}. \]

Prove \( E \leq G \).

Prove any subgroup of a cyclic group is itself a cyclic group.
Transcribed Image Text:Let \( G \) and \( H \) be two groups, \( \phi, \psi \in \text{Hom}(G, H) \), and \( A \subset G \) be a nonempty subset. (a) Prove \[ \phi(\langle A \rangle) = \langle \phi(A) \rangle. \] Here, \( \langle A \rangle \) denotes the subgroup generated by \( A \). (b) Let \[ E = \{ a \in G : \phi(a) = \psi(a) \}. \] Prove \( E \leq G \). Prove any subgroup of a cyclic group is itself a cyclic group.
Expert Solution
Step 1

We have proved (a) in two steps, showing both the subset relation one by one.

For (b) we have used the theorem that to prove H is a subgroup of G we need to prove ab^{-1} belong to H for all a,b in H.

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