At time t = 0, a particle is located at the point (9,4,7). It travels in a straight line to the point (4,7,2), has speed 5 at (9,4,7) and constant acceleration - 5i + 3j - 5k. Find an equation for the position vector r(t) of the particle at time t. The equation for the position vector r(t) of the particle at time t is r(t) = (Ji+ (]) j+ () k. (Type exact answers, using radicals as needed.)