In: Advanced Math
Let f be a group homomorphism from a group G to a group H
If the order of g equals the order of f(g) for every g in G must f be one to one.
be a group homomorphism .
Suppose be two elements . Now ,
, where is the identity elemnt of H .
, As f is a homomorphism .
As given order of equals to so order of is equals to order of
Order of = Order of
Now as order of the identity element is always 1 so ,
Order of is 1 .
As only identity can have order 1 so ,
So implies .
Hence is one-to-one.
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If you have any doubt or need more clarification at any step please comment.