Let G he an abelian group and H g G ordg is finite Show th
Let G he an abelian group and H = {g G | ord(g) is finite}. Show that H is a subgroup of G.
Solution
The start: let a^m=b^n=1. Then (ab)^mn=1.
Let H be the set of all elements of finite order.
(gh)^nm=(g)^nm . (h)^nm = (g^n)^m . h(^m)^n = 1^m .1^n=1.
(g1)^n. g^n=1=(g1)^n.
Therefore, H is a subgroup.
