Fix for broken equation

docs/Chapters/1-MODERN-CONTROL.md

@@ -107,21 +107,24 @@ $$
 >
 > Then, put all variables equal to the previous one derivated:
 >
-> $x(t) =  \begin{bmatrix}
->             x_1(t)\\
->             x_2(t) = \dot{x_1}(t)\\
->             \dots\\
->             x_n(t) = \dot{x}_{n-1}(t)
->         \end{bmatrix}
-> \;
-> \dot{x}(t) =  \begin{bmatrix}
->             \dot{x_1}(t) = x_2(t)\\
->             \dot{x_2}(t) = x_3(t)\\
->             \dots\\
->             \dot{x}_{n-1}(t) = \dot{x}_{n}(t)\\
->             \dot{x}_{n}(t) = \text{our formula}
->         \end{bmatrix}$
-> 
+$$
+x(t) =  \begin{bmatrix}
+            x_1(t)\\
+            x_2(t) = \dot{x_1}(t)\\
+            \dots\\
+            x_n(t) = \dot{x}_{n-1}(t)
+        \end{bmatrix}
+\;
+\dot{x}(t) =  \begin{bmatrix}
+            \dot{x_1}(t) = x_2(t)\\
+            \dot{x_2}(t) = x_3(t)\\
+            \dots\\
+            \dot{x}_{n-1}(t) = \dot{x}_{n}(t)\\
+            \dot{x}_{n}(t) = \text{our formula}
+        \end{bmatrix}
+
+$$
+
 
 Now in our state we may express `position` and `speed`, while in our 
 `next_state` we'll have `speed` and `acceleration`: