A particle moves in a straight line so that its velocity at time t t\,t seconds, t≥0t \geq 0t≥0, is v=(3t2−12t+9)v = (3t^2 - 12t + 9)v=(3t2−12t+9) m s−1^{-1}−1
Find the acceleration of the particle when t=1t = 1t=1.
Find the times at which the particle is instantaneously at rest.