Answer to Question #140394 in Abstract Algebra for J

Question #140394
state what properties you use/defintions/etc...

Let (G,✳) be a group, and let a∈G. Let C(a) = {g∈G: a✳g = g✳a}.

In this problem we will prove that (C(a),✳) is a subgroup of (G,✳).

C(a)⊆G by the definition of C(a).
1
Expert's answer
2020-10-26T20:08:31-0400

Solution

C(a)C(a) is not empty since eG\exist e \in G such that ae=eaa *e=e*a so eC(a)e\in C(a) (where e is the identity element of G)

Since C(a)GC(a)\subseteq G then C(a)C(a) is associative under the operation * .

Let x,yC(a)x,y\in C(a), then ax=xaa*x=x*a and ay=yaa*y=y*a

axy=a(xy)=(xy)aa*x*y=a*(x*y) =(x*y)*a (by definition) so (xy)C(a)(x*y)\in C(a)

Since eC(a)e \in C(a) we have ae=a(xx1)=(ax)x1a*e=a*(x*x^{-1}) = (a*x)*x^{-1} and ea=(x1x)a=x1(xa)e*a=(x^{-1}*x)*a= x^{-1}*(x*a) which implies that x1C(a)x^{-1}\in C(a)

Therefore (C(a),)(C(a),*) is a subgroup of the group (G,)(G,*) .



Need a fast expert's response?

Submit order

and get a quick answer at the best price

for any assignment or question with DETAILED EXPLANATIONS!

Comments

No comments. Be the first!

Leave a comment