in the particle under constant acceleration model we identify the variables and parameters Vxi, Vxf, ax, t, and xf-xi. Of the equations in the model, Equations 2.13-2.17, the first does not involve xf-x, the second and third do not contain ax, the fourth omits Vxf, and the last leaves out t. So, to complete the set, there should be an equation not involving Vxi. Derive it from the others.