Update textbook.fr.md

01.curriculum/01.physics-chemistry-biology/03.Niv3/05.math-tools-for-physics/04.differential-operators/04.curl/textbook.fr.md

@@ -188,7 +188,7 @@ $`\displaystyle \overrightarrow{X_R}=\left[X_M +
 \left.\dfrac{\partial X}{\partial x}\right|_M \cdot 
 \left(+\dfrac{dx}{2}\right)\right] \cdot \overrightarrow{e_x}`$
 $`+\left[Y_M+\left.\dfrac{\partial Y}{\partial x}\right|_M \cdot 
-\left(+\dfrac{dx}{2}\right)\right] \cdot \overrightarrow{e_y}$`
+\left(+\dfrac{dx}{2}\right)\right] \cdot \overrightarrow{e_y}`$
 $`+\left[Z_M+\left.\dfrac{\partial Z}{\partial x}\right|_M \cdot 
 \left(+\dfrac{dx}{2}\right)\right] \cdot \overrightarrow{e_z}`$