udpates?

content/Math4302/Math4302_L5.md

@@ -80,7 +80,7 @@ $D_n\leq S_n$ ($S_n$ is the symmetric group of $n$ elements).
 
 If $H\subseteq G$ is a non-empty subset of a group $G$.
 
-then ($H$ is a subgroup of $G$) if and only if ($a,b\in H\implies ab^-1\in H$).
+then ($H$ is a subgroup of $G$) if and only if ($a,b\in H\implies ab^{-1}\in H$).
 
 <details>
 <summary>Proof</summary>