# Powers of Group Elements/Sum of Indices/Additive Notation

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## Theorem

Let $\struct {G, +}$ be a group whose identity is $e$.

Let $g \in G$.

Then:

$\forall m, n \in \Z: m g + n g = \paren {m + n} g$

## Proof

All elements of a group are invertible, so we can directly use the result from Index Laws for Monoids: Sum of Indices:

$\forall m, n \in \Z: g^m \circ g^n = g^{m + n}$

where in this context the group product operator is $+$ and $n$th power of $g$ is denoted $n g$.

$\blacksquare$