Let $G$ be a finite group of order $2n$ for some integer $n$. Consider the map $\phi : G \rightarrow G$ given by $\phi(a) = a^2$. Show that $\phi$ is not surjective.
Let $G$ be a finite group of order $2n$ for some integer $n$. Consider the map $\phi : G \rightarrow G$ given by $\phi(a) = a^2$. Show that $\phi$ is not surjective.