the 3rd kine eqns, p3
- Rearrange of (I5) will produce $$\tag{I6} \begin{array}{rcl} 2a(x - x_0) & = & (v_0 + v)(v - v_0) \\[0.5em] (v + v_0)(v - v_0) & = & 2a(x - x_0) \\[0.5em] v^2 - v_0^2 & = & 2a(x - x_0) \\[0.5em] v^2 & = & v_0^2 + 2a(x - x_0), \end{array} $$ which is the third kinematics equation.