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Previous Year Question (PYQs)



Let $(Z,+)$ denote the group of all integers under addition. Then the number of all automorphisms of $(Z,+)$ is





Solution

An automorphism of $(Z,+)$ is completely determined by the image of $1$.

The image of $1$ must be a generator of $Z$.

The generators of $Z$ are:

$1$ and $-1$

So, there are only two automorphisms:

$f(n)=n$

$f(n)=-n$


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