Fix for broken equation

docs/Chapters/1-MODERN-CONTROL.md

@@ -107,23 +107,20 @@ $$
 >
 > Then, put all variables equal to the previous one derivated:
 >
-> $$
-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