Equations (5) form a system of ordinary second-order differential equations with unknowns . Their form is invariant with respect to the choice of Lagrange coordinates. This system of equations of motion has least possible order . In this respect, and ... in the absence of reactions of the constraints in (5), equations (5) have a great advantage compared to Lagrange's equations of the first kind (3). After integrating (5) one can determine the reactions of the constraints from the equations that express Newton's second law for the points of the system (cf. also Newton laws of mechanics).