Update textbook.fr.md

00.brainstorming-pedagogical-teams/40.collection-existing-pedagogical-content/40.classical-mechanics/10.main/textbook.fr.md

@@ -274,12 +274,14 @@ $`\mathbf{
 \left\{\begin{array}{l}
 t'=dt \\
 \dfrac{dx'}{dt'}=\dfrac{dx}{dt}-V_x \\
+\\
 \dfrac{dy'}{dt'}=\dfrac{dy}{dt}-V_y \\ 
+\\
 \dfrac{dz'}{dt'}=\dfrac{dz}{dt}-V_z 
 \end{array}
 \right.
 }`$
-$`\quad\Longrightarrow`$
+$`\quad\Longrightarrow\quad`$
 $`\mathbf{
 \left\{\begin{array}{l}
 v_x'=v_x-V_x \\