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Ques-6-Let-G-be-a-group-and-let-C-c-G-c-a-a-c-a-G-Prove-that-C-is-subgroup-of-G-hence-or-otherwise-show-that-C-is-Abelian-Note-C-is-called-the-center-of-group-G-Ques-7-




Question Number 193804 by Mastermind last updated on 20/Jun/23
Ques. 6        Let (G, ∗) be a group. and let  C={c∈G : c∗a = a∗c ∀a∈G}. Prove  that C is subgroup of G. hence or   otherwise show that C is Abelian.    [Note C is called the center of group G]    Ques. 7       If (G, ∗) is a group such that (a∗b)^2    = a^2 ∗b^2  (multiplicatively) for all   a,b∈G. Show that G must be Abelian
Ques.6Let(G,)beagroup.andletC={cG:ca=acaG}.ProvethatCissubgroupofG.henceorotherwiseshowthatCisAbelian.[NoteCiscalledthecenterofgroupG]Ques.7If(G,)isagroupsuchthat(ab)2=a2b2(multiplicatively)foralla,bG.ShowthatGmustbeAbelian
Answered by Rajpurohith last updated on 20/Jun/23
  (7)I shall omit the notation ∗.  i.e, By ab I mean a∗b.  Given that (ab)^2 =a^2 b^2       ∀a,b∈G  ⇒(ab)(ab)=aabb                  ∀a,b∈G  ⇒abab=aabb                         ∀a,b∈G  ⇒a^(−1) (abab)b^(−1) =a^(−1) (aabb)b^(−1)    ∀a,b∈G  ⇒ba=ab    ∀ a,b∈G  ⇒G is Abelian.      ■
(7)Ishallomitthenotation.i.e,ByabImeanab.Giventhat(ab)2=a2b2a,bG(ab)(ab)=aabba,bGabab=aabba,bGa1(abab)b1=a1(aabb)b1a,bGba=aba,bGGisAbelian.◼
Commented by Mastermind last updated on 20/Jun/23
Thank you so much, God will bless you Inshallah
Thankyousomuch,GodwillblessyouInshallah
Answered by gatocomcirrose last updated on 20/Jun/23
Note that e∈C since e∗a=a∗e, ∀a∈G⇒C≠∅  Let x, y∈C,  ⇒x∗a=a∗x⇒a=x^(−1) ∗a∗x⇒a∗x^(−1) =x^(−1) ∗a, ∀a∈G  ⇒x^(−1) ∈G  (x∗y)∗a=x∗(y∗a)=x∗(a∗y)=(x∗a)∗y  =(a∗x)∗y=a∗(x∗y), ∀a∈G⇒x∗y ∈G    Then C<G (subgroup).    Let x,y∈C, since C<G∴x,y∈G  (x∈C)⇒x∗a=a∗x, ∀a∈G  for a=y∈G⇒x∗y=y∗x⇒C is abelian
NotethateCsinceea=ae,aGCLetx,yC,xa=axa=x1axax1=x1a,aGx1G(xy)a=x(ya)=x(ay)=(xa)y=(ax)y=a(xy),aGxyGThenC<G(subgroup).Letx,yC,sinceC<Gx,yG(xC)xa=ax,aGfora=yGxy=yxCisabelian
Commented by Mastermind last updated on 20/Jun/23
Thank you my man
Thankyoumyman

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