Fixed Parsing errors

Signed-off-by: chris-admin <chricchio.risi@icloud.com>

docs/Chapters/1-MODERN-CONTROL.md

@@ -12,9 +12,7 @@ right being its tranformation in the complex domain field.
 
 > [!NOTE]
 >
-> $$
+> $\dot{x}(t) = ax(t) + bu(t) \longleftrightarrow x(k+1) = ax(k) + bu(k)$
-> \dot{x}(t) = ax(t) + bu(t) \longleftrightarrow x(k+1) = ax(k) + bu(k)
-> $$
 >
 > These are equivalent, but the latter one is in discrete time.
 >