Final answer:
The particle is moving to the right for values of t less than the positive constant a.
Step-by-step explanation:
The particle is moving to the right when its velocity is positive. To determine the values of t for which the particle is moving to the right, we need to find the values of t when the velocity is positive.
The velocity function is the derivative of the position function. In this case, the position function is x(t) = (1/2)(a-t)^2 and the velocity function is v(t) = -2(a-t). We know that v(t) > 0 when -2(a-t) > 0. Solving this inequality, we find that t < a. Therefore, the particle is moving to the right for values of t less than the positive constant a.